Brock Biology of Microorganisms 16th Edition
Madigan Test Bank
Brock Biology of Microorganisms, 16e (Madigan et al.)
Chapter 1 The Microbial World
1.1 Multiple Choice Questions
1) Which of the following statements is FALSE?
A) Microbial cells can exist as single cells.
B) Microbial cells carry out their life processes of growth independently.
C) Microbial cells include both bacteria and viruses.
D) Microbial cells are surrounded by a cytoplasmic membrane.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
2) Which of the following statements is correct?
A) Microorganisms are significant contributors to the total biomass on Earth.
B) Microorganisms represent a much smaller amount of Earth's biomass than plants.
C) Microorganisms represent a much smaller amount of Earth's biomass than animals.
D) Microorganisms are significant in number, but not in overall biomass.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.1
Learning Objective: 1.I
3) Differential selection and decent with modification occurs during a process called
A) cellular differentiation.
B) evolution.
C) growth.
D) transformation.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
4) In what/which domain(s) of life is/are microorganisms represented?
A) Archaea
B) Bacteria
C) Eukarya
D) Archaea, Bacteria, and Eukarya
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
1
Chapter Section: 1.4
Learning Objective: 1.I
5) Biological catalysts involved in the acceleration of the rate of chemical reactions are called
A) catalytic converters.
B) growth agents.
C) evolutionary molecules.
D) enzymes.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
6) Regarding early life on Earth,
A) microbial life existed for billions of years before plant and animal life.
B) microbial life existed long before animals but has been around for about the same amount of
time as plants.
C) microbial life, plant life, and animal life all appeared at about the same time.
D) it is impossible to determine which type of life first appeared.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
7) The person who described the "wee animalcules" was
A) Robert Hooke.
B) Antoni van Leeuwenhoek.
C) Louis Pasteur.
D) Ferdinand Cohn.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.7
Learning Objective: 1.II
8) Walther Hesse and
pioneered the use of agar as a solidifying agent.
A) Louis Pasteur
B) Ferdinand Cohn
C) Robert Koch
D) Sergei Winogradsky
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
2
9) Which of the following is/are characteristic of all cellular organisms?
A) Communication
B) Evolution
C) Motility
D) Communication, evolution, and motility
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
10) Deduce why viruses are excluded from the ribosomal RNA-based tree of life.
A) Some viruses contain multiple strands of RNA.
B) Their genetic elements cannot be sequenced.
C) They can infect other organisms, which complicates the genetic comparisons.
D) They lack ribosomal RNA (rRNA).
Answer: D
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.15
Learning Objective: 1.IV
11) Louis Pasteur developed the vaccine(s) for
A) anthrax only.
B) fowl cholera only.
C) rabies only.
D) anthrax, fowl cholera, and rabies.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
12) The discovery of antibiotics and other important chemicals led to the field of
A) industrial microbiology.
B) agricultural microbiology.
C) marine microbiology.
D) aquatic microbiology.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
3
13) Microbial sterilization is used to
A) decrease the possibility of contaminants growing in a culture.
B) kill bacteria but not necessarily viruses or other microbes.
C) kill all microbes in or on objects.
D) clean a work area.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
14) Transparent double-sided dishes used for growing microbes are most commonly called
A) Petri dishes.
B) baker dishes.
C) sterilization plates.
D) culture medium plates.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
15) Microbes playing a role in nitrogen fixation in plants live in
role in the digestive tract of certain herbivores live in
.
A) rumens / nodules
B) nodules / rumens
C) nodules / fortrans
D) fortrans / rumens
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
, while those playing a
16) Which of the following is NOT an accomplishment of Louis Pasteur?
A) Determined that the alcohol-making process was mediated by microbial fermentation and
thus refuted the theory of spontaneous generation
B) Developed enrichment culture techniques
C) Developed heat sterilization techniques that involved the creation of a specialized swannecked flask
D) Developed the first rabies vaccine and treated thousands of individuals
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
4
17) The theory of spontaneous generation was refuted by the work of
A) Louis Pasteur.
B) Robert Koch.
C) Robert Hooke.
D) Antoni van Leeuwenhoek.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
18) A Pasteur flask has a(n)
A) swan neck to prevent particulate matter from getting into the main body of the flask.
B) double neck so two substances may be added at the same time.
C) secondary opening at the base to allow for drainage.
D) inverted upper edge to prevent spillage while swirling.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
19) Predict how Pasteur's conclusions on spontaneous generation with swan flasks would have
changed if he worked with and maintained the flasks in a sterile laminar flow hood.
A) Sterilization of the swan flask solutions would not have been necessary to reject spontaneous
generation. If he did sterilize the flasks, the spontaneous generation hypothesis would have been
supported.
B) His incubation times would not have been sufficient to refute spontaneous generation.
C) Pasteur's flasks never would have putrefied, and the experiment would not have refuted
spontaneous generation.
D) Viruses would have still been present, and his conclusion would have been unchanged.
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.11
Learning Objective: 1.III
20) A pure culture
A) is sterile.
B) is a population of identical cells.
C) is made of a clearly defined chemical medium.
D) contains one microbial cell.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
5
21) Martinus Beijerinck was the first to isolate
A) green algae.
B) certain nitrogen-fixing root nodule bacteria.
C) certain sulfate-reducing bacteria.
D) green algae, certain nitrogen-fixing root nodule bacteria, and certain sulfate-reducing bacteria.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.13
Learning Objective: 1.III
22) Chemolithotrophy involves
A) oxidation of organic compounds.
B) oxidation of inorganic compounds.
C) reduction of organic compounds.
D) metabolic autotrophy.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.13
Learning Objective: 1.III
23) Developments in the fields of immunology and medical microbiology were practical
extensions of the work of
A) Sergei Winogradsky.
B) Antoni van Leeuwenhoek.
C) Joseph Lister.
D) Robert Koch.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
24) Microbial control in wastewaters would most logically be a part of
A) microbial genetics.
B) aquatic microbiology.
C) medical microbiology.
D) bacterial energetics.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
6
25) Robert Koch contributed to the field of microbiology by being the first person to
A) develop the tuberculin test only.
B) formulate four postulates for definitively linking a specific microorganism to a specific
disease only.
C) use agar as a solidifying agent in growth media only.
D) develop the tuberculin test, formulate four postulates for definitively linking a
specific microorganism to a specific disease, and use agar as a solidifying agent in growth
media.Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
26) Mycobacterium tuberculosis is very difficult to stain because of the
A) presence of ribosomes in the cytoplasm.
B) location of the DNA within the cell.
C) large amounts of a waxlike lipids present in its cell wall.
D) lack of a cell wall.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
27) Louis Pasteur's most famous success was his work on
A) Mycobacterium tuberculosis.
B) the rabies vaccine.
C) optical isomers.
D) cultivation of E. coli.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.11
Learning Objective: 1.III
28) Microorganisms play key roles in the cycling of important nutrients in plant nutrition,
particularly those of
A) carbon only.
B) nitrogen only.
C) sulfur only.
D) carbon, nitrogen, and sulfur.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
7
29) Microbial ecology is the study of
A) microbial processes in the rhizosphere that benefit plant growth.
B) the diversity and activities of microorganisms.
C) the grouping and classifying of microorganisms.
D) microorganisms in their natural environments.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
30) The structure that confers structural strength on the cell is known as the
A) cytoplasmic membrane.
B) cell wall.
C) ribosome.
D) cytoplasm.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
31) A microbial cell's membrane is considered
, because its internal constituents are
maintained within the cell. However, it also imports and exports other molecules in response to
its environment.
A) differential
B) microselective
C) rigid
D) semipermeable
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
32) Some microorganisms can undergo
in which various cell types can become
specialized and arise from one parent cell type.
A) differentiation
B) genetic exchange
C) maturation
D) mutagenesis
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
8
33) Cyanobacteria and purple sulfur bacteria both obtain energy from light. However, only the
are capable of releasing
.
A) cyanobacteria / organic compounds
B) cyanobacteria / oxygen
C) purple bacteria / organic compounds
D) purple bacteria / oxygen
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
34) The process whereby microorganisms are used to help clean up pollution created by human
activities is known as
A) bioaugmentation.
B) biodegradation.
C) bioengineering.
D) bioremediation.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
35) Robert Koch received the 1905 Nobel Prize in Physiology or Medicine for
A) developing a smallpox vaccination.
B) identifying Mycobacterium tuberculosis as the causative agent of tuberculosis.
C) making an effective rabies vaccine.
D) developing a smallpox vaccination, identifying Mycobacterium tuberculosis as the causative
agent of tuberculosis, and making an effective rabies vaccine.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
36) Bacillus anthracis deficient in its ability to differentiate would not be able to
A) chemotax toward growth substrates.
B) create vesicles.
C) form spores.
D) grow without additional supplemented nutrients.
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.3
Learning Objective: 1.I
9
37) Microbial biochemistry most specifically involves the discovery of microbial
the
they perform.
A) organelles / diffusion
B) enzymes / organelles
C) reactions / enzymes
D) macromolecules / functions
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.14
Learning Objective: 1.IV
38) Microbial cells first evolved on Earth approximately
A) 1.6 to 1.8
B) 3.8 to 4.3
C) 5.4 to 5.6
D) 7.0 to 7.2
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
39) The first documented description of a microorganism was of a
A) bacterium / Ferdinand Cohn
B) fungus / Robert Koch
C) mold / Robert Hooke
D) yeast / Martinus Beijerinck
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.7
Learning Objective: 1.II
and
billion years ago.
_ by
.
40)
produced by microbial fermentation of glucose from cellulose or cornstarch is
becoming a more important component of biofuels in the United States, and specialized
are needed to make this a commercially available product.
A) Biodiesel / biotechnologists
B) Biodiesel / industrial microbiologists
C) Ethanol / biotechnologists
D) Ethanol / industrial microbiologists
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
10
41)
was the first to describe microorganisms, while
see bacteria.
A) Antoni van Leeuwenhoek / Robert Hook
B) Antoni van Leeuwenhoek / Robert Koch
C) Robert Hooke / Antoni van Leeuwenhoek
D) Robert Koch / Antoni van Leeuwenhoek
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.7
Learning Objective: 1.II
was the first person to
42) The production of human proteins (e.g., insulin) by genetically engineered microorganisms is
an example of
, a subdiscipline of microbiology.
A) applied microbiology
B) biotechnology
C) industrial microbiology
D) molecular microbiology
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.6
Learning Objective: 1.I
43) Approximately two billion years ago,
_ were primarily responsible for initially
oxygenating Earth.
A) algae
B) Archaea
C) cyanobacteria
D) purple sulfur bacteria
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
44) Archaea and Bacteria are unified as prokaryotes in lacking
contain, such as mitochondria.
A) membranes
B) nuclei
C) membrane-enclosed organelles
D) nuclei and membrane-enclosed organelles
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.4
Learning Objective: 1.I
11
which Eukarya
45) Bioremediation
by introducing pollutant-consuming microorganisms or specific
nutrients that help microorganisms degrade pollutants.
A) accelerates the natural cleanup process
B) exploits genetic exchange mechanisms
C) invokes microbial evolution
D) uses chemotaxis of biodegrading microorganisms
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
46) Electron microscopy has greater
than light microscopy, because the wavelength of
visible light is much larger than the wavelength of electrons.
A) contrast
B) magnification
C) resolution
D) penetration
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
47) Which of the following types of microscopy is especially effective for viewing details of
internal structures within live cells?
A) Phase-contrast microscopy
B) Transmission electron microscopy
C) Bright-field microscopy
D) Scanning electron microscopy
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.8
Learning Objective: 1.II
48) Which of the following types of microscopy could be used to visualize the layers of the cell
membrane and the cell wall?
A) Phase-contrast microscopy
B) Transmission electron microscopy
C) Bright-field microscopy
D) Confocal microscopy
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
12
49) Who was the first researcher to provide direct experimental data that supported the germ
theory to explain infectious disease?
A) Pasteur
B) Winogradsky
C) Lister
D) Koch
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
50) When medical devices are left in the body, bacteria may grow on them as
makes them especially resistant to treatment.
A) biofilms
B) liquids
C) populations
D) communities
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
, which
51) Microbes that live at high temperatures in hot springs are
A) always Archaea.
B) also able to thrive at low temperatures.
C) called extremophiles.
D) rarely found.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
52) What field focuses specifically on the use of microbes to make products, such as antibiotics,
on a large scale?
A) Microbial ecology
B) Biotechnology
C) Industrial ecology
D) Medical microbiology
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
13
53) Which statement about the relationship between microbes and humans is FALSE?
A) Most microbes are pathogenic.
B) Infectious disease is an important public health concern.
C) Bacteria in the digestive tract are important for digestion.
D) Microbes in root nodules fix nitrogen and allow plants to make nitrogen-rich products.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
54) Why is ribosomal RNA especially useful for the study of phylogenetic relationships?
A) It is only found in some species, helping them to distinguish from others.
B) It is highly conserved.
C) It is highly variable.
D) It is extremely short.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.15
Learning Objective: 1.IV
55) Why is it important to use cultivation-independent methods to help understand microbial
diversity?
A) It allows researchers to identify species that cannot be grown in culture.
B) It is the only way that phylogenetic trees can be constructed.
C) It must be used after bacteria are cultured to more fully sequence their DNA.
D) It is necessary to be able to examine ribosomal RNA.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.15
Learning Objective: 1.IV
56) Compared to Eukaryotes, Bacteria and Archaea have
causing
nutrient exchange.
A) lower / lower
B) lower / higher
C) higher / lower
D) higher / higher
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.3
Learning Objective: 1.I
14
surface-to-volume ratios,
57) An organism of the genus Staphylococcus is _
Spirochaeta is
.
A) spherical / rod shaped
B) rod shaped / coiled
C) spherical / coiled
D) coiled / spherical
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.3
Learning Objective: 1.I
, while an organism of the genus
58) The morphology of a cell influences its
A) motility.
B) metabolism.
C) surface-to-volume ratio.
D) motility and surface-to-volume ratio.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.3
Learning Objective: 1.I
59) You have discovered a new microorganism and would like to classify it as a eukaryote or a
prokaryote. To investigate this question, you prepare a slide with a simple stain and view it with
a light microscope with a 40X objective lens and 10X ocular lens. You also prepare a control
slide using Saccharomyces cerevisiae (a unicellular eukaryote). You can see the cells on your
control slide, but you don't see cells when you look at your unknown microorganism. What can
you conclude from this experiment?
A) The experiment failed to visualize the organism because the stain killed it.
B) Your new unknown microorganism is probably a virus.
C) The cells of the new unknown microorganism may be too small to see with the objective and
ocular lenses you used.
D) The new unknown microorganism is probably an archaeon.
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.7
Learning Objective: 1.II
60) Aseptic technique refers to
A) the microbial inoculum placed into a test tube or onto a Petri plate.
B) a series of practices to avoid contamination.
C) the autoclave and other sterilizing procedures.
D) cleanliness in the laboratory.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
15
1.2 True/False Questions
1) Most microorganisms are pathogenic.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
2) All microorganisms require molecular oxygen to carry on life functions.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
3) Metabolism is a unifying characteristic of all cellular organisms.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
4) According to our present understanding, each of the three major domains has what is known
as its own universal ancestor.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.4
Learning Objective: 1.I
5) Both environmental conditions and nutrient resources strongly influence the composition of a
microbial community.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.1
Learning Objective: 1.I
6) The environment in which a microbial population lives is called its habitat.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
7) Differentiation occurs only in multicellular organisms.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
16
8) The discipline of microbiology is intimately associated with biochemistry and genetics,
because cells are both biochemical catalysts and genetic coding devices.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.14
Learning Objective: 1.IV
9) Today, the enrichment culture technique developed over a century ago by Martinus Beijerinck
remains a feasible approach to discovering bacteria capable of degrading pollutants.
Answer: TRUE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.13
Learning Objective: 1.III
10) Sergei Winogradsky worked with bacteria involved in cycling nitrogen and sulfur.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.13
Learning Objective: 1.III
11) Treponema pallidum, a bacterium associated with syphilis, is not considered a pathogen
because to date it remains unculturable in the lab, and, therefore, Koch's postulates are unable to
be fulfilled.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.12
Learning Objective: 1.III
12) Not only do some microorganisms tolerate extremely hot temperatures, some actually require
high temperatures for optimal growth.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.4
Learning Objective: 1.I
13) Electron microscopes have less resolving power (resolution) than light microscopes.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
14) Smaller prokaryotic cells generally grow faster than larger ones due to a higher surface-areato-volume ratio.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.3
Learning Objective: 1.I
17
15) A bacterial cell is interpreted as gram-positive when it forms purple insoluble crystal violetiodine complexes within the cell during the Gram stain.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.8
Learning Objective: 1.II
16) Viewing the shape of a bacterial or archaeal cell using a microscope gives a great deal of
information about the metabolism and lifestyle of the organism.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.8
Learning Objective: 1.II
1.3 Essay Questions
1) Explain the nature and function of an enrichment culture.
Answer: Answers will vary, but an enrichment culture uses media, chemicals, or culture
conditions to select for or encourage the growth of organisms with specific characteristics. An
answer could describe providing only carbon dioxide as a source of carbon to select for
autotrophs, for example.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
2) Why is it incorrect to say that an object is partially sterile?
Answer: Sterile means the absence of all living organisms. Something is either sterile or it is
not.
Other terms are used to describe objects that have been cleaned but are not sterile, such as
disinfected.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.10
Learning Objective: 1.II
3) Microbes were first formally observed during the mid-1600s, but the cell theory was not
enunciated until 1839. Write a brief essay explaining why microbiology did not become a
formally recognized science until Louis Pasteur's and Robert Koch's time.
Answer: Answers will vary, but a theme should be the lack of powerful microscopy tools.
Without sufficient microscopes, individual cells could not be seen but the activities of
microorganisms could be observed, such as the production of ethanol in Louis Pasteur's
experiments on fermentation.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.11, 1.12
Learning Objective: 1.III
18
4) Compare and contrast the works of Louis Pasteur and Robert Koch in terms of both applied
techniques and basic science.
Answer: Answers will vary, but should highlight the differences between basic scientific
research in which fundamental ideas are discovered opposed to the usage of microbiological
principles to solve larger questions. Examples of Pasteur's basic science contributions are his
work showing that fermentation was mediated by microorganisms and the preferential
metabolism of particular optical isomers by microbes. Pasteur also applied his ideas to develop
sterilization techniques. Robert Koch focused more on the application of microbiology to
identify the cause of tuberculosis by developing pure culturing techniques and the four postulates
to link microbes to a disease.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.11, 1.12
Learning Objective: 1.III
5) Explain why microbial cells are excellent models for understanding cell function in higher
organisms.
Answer: Answers will vary, but should include commonality of function, biochemical and
genetic similarities, and ease and speed with which they can be grown in large quantities.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
6) Compare and contrast the leading causes of death in 1900 with the leading causes of death
today. What roles have microbiologists played in the dramatic changes that are evident?
Answer: Answers will vary, but a focus should be that pathogens that killed people in the early
1900s are now treatable due to knowledge learned from microbiologists.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.6
Learning Objective: 1.I
7) Explain how you would use Robert Koch's postulates to determine that Streptococcus
pyogenes is the causative agent of streptococcal pharyngitis ("strep throat").
Answer: Answers will vary but will need to detail how S. pyogenes will be subjected to all four
postulates.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.12
Learning Objective: 1.III
8) Describe beneficial and harmful ways in which microorganisms interact with agricultural
crops.
Answer: Certain microbes are beneficial to crops when they produce nutrients (e.g., NH4+,
SO42−) usable by a crop from a substrate that was unusable. Other microbes can cause diseases
in plants, much like pathogens cause disease in humans.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
19
9) Provide evidence supporting the statement that an "ecosystem is controlled by microbial
activities."
Answer: Answers will vary, but one example could be oxygen depletion, where a loss of oxygen
would then favor anaerobic microorganisms.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.5, 1.6
Learning Objective: 1.I
10) Explain why only anaerobic bacteria inhabited Earth for the first two billion years of its
existence.
Answer: The key idea is an anoxic environment will not allow aerobic organisms to survive.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.5
Learning Objective: 1.I
11) Using specific examples, explain why it is sometimes impossible to satisfy Robert Koch's
postulates.
Answer: Answers will vary, but one issue is the consideration for a model animal host that will
react to the (human) pathogen in the same manner as in a human host. For example, a chicken
would not show flu-like symptoms when infected with the influenza virus. Another issue is the
inability to cultivate some microorganisms outside of the host.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.12
Learning Objective: 1.III
12) Explain why infectious diseases are much less lethal in developed countries than in
underdeveloped countries.
Answer: Answers will vary, but should emphasize ways in which increased knowledge about
microbial pathogenesis has influenced preventative care (e.g., sanitation) and treatment (e.g.,
antimicrobial drugs).
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.6
Learning Objective: 1.I
13) Describe two capabilities of microbes that exemplify their dynamic nature in interacting with
their environment.
Answer: Answers could possibly include cell-cell communication, ability to move (motility),
ability to differentiate, and exchange of materials (any two).
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 1.2
Learning Objective: 1.I
20
14) Compare and contrast the functions microbes serve in the digestive systems of both humans
and ruminants (e.g., cattle).
Answer: Answers will vary, but should focus on humans having a high cell localized density in
the colon (large intestine), whereas rumens have higher microbial populations in the rumen.
Microbes in both systems aid in digestion and improve nutrition/health of the host.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 1.6
Learning Objective: 1.I
15) The explosive chemical trinitrotoluene (TNT) can remain in soils after use and is hazardous
to humans. Propose an experiment in which TNT-degrading microorganisms could be isolated
for purposes of bioremediation. Also, indicate what experimental evidence would be useful to
isolate TNT-degrading microorganisms.
Answer: Experimental designs will vary, but one example would be to use the enrichment
culture technique with soil from an ammunition site. While adding TNT to the enrichment
culture, a key piece of experimental evidence could be the loss of TNT in the culture to initiate
isolation attempts.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.6
Learning Objective: 1.I
16) What type of microscope would you use to visualize the internal structures of a chloroplast?
Support your answer with evidence based on the size of the structures you want to see and the
resolution and magnification power of different types of microscopes.
Answer: Transmission electron microscopy would be necessary to visualize the internal
structures of a chloroplast. Chloroplasts are less than 5 μm in diameter and the internal
membranes are only 10 nm thick. Light microscopes only have a resolution of 200 nm, thus any
structure less than 200 nm will not be visible. Individual chloroplasts could be seen with a light
microscope, but not the structures inside. Scanning electron microscopy can only see external
features because electrons cannot penetrate the cell, thus the cell must be sectioned and prepared
for transmission electron microscopy to see the inside of the chloroplasts.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.10
Learning Objective: 1.II
17) Explain why prokaryotes tend to survive and adapt more rapidly to extreme and dynamic
environmental conditions than eukaryotes.
Answer: Answers will vary, but should reflect an understanding of how the higher surface-tovolume ratio influences the growth rate and total accumulation of mutations in prokaryotes.
Another feature that increases mutation rate is the haploid nature of prokaryotes. Lastly, answers
could mention that the rigid cell walls and various changes in the cytoplasmic membrane make it
easier for prokaryotes to survive in unusual and extreme environments.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.2
Learning Objective: 1.I
21
18) Explain why being small is advantageous for cells and how it affects growth rates.
Answer: A smaller cell has a greater surface area to volume ratio than a larger cell. This means
that smaller cells can more rapidly exchange materials with their surroundings because there is
so much surface membrane relative to the internal volume. This increases growth rates, meaning
that smaller cells generally grow faster than larger cells.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 1.2
Learning Objective: 1.I
22
Brock Biology of Microorganisms, 16e (Madigan et al.)
Chapter 2 Microbial Cell Structure and Function
2.1 Multiple Choice Questions
1) Bacteria with type IV pili
A) possess tubular or stalk-like extensions of their cells.
B) likely exhibit twitching motility.
C) have capsules that promote dehydration.
D) live in aquatic environments.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.6
Learning Objective: 2.II
2) The terms "run" and "tumble" are generally associated with
A) eukaryotic cells.
B) nutrient transport.
C) chemotaxis.
D) clustering of certain rod-shaped bacteria.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.11
Learning Objective: 2.III
3) The cytoplasmic membrane could best be described as
A) an impermeable barrier.
B) a passive conduit for intracellular transport.
C) a highly selective permeability barrier.
D) a rigid structure that protects the cell.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
4) The use of the Gram stain in microbiology is important because it differentiates
A) Bacteria from Archaea.
B) prokaryotic from eukaryotic cells.
C) bacterial cells with different types of cell walls.
D) archaeal cells with different types of metabolism.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
1
5) Some archaea have unique phospholipids in their cytoplasmic membrane that
A) form a monolayer due to the presence of diglycerol tetraethers.
B) form a bilayer due to the presence of sterols.
C) form a stable ring structure due to the presence of crenarchaeol.
D) form a bilayer due to the presence of phosphatidylethanolamine.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
6) Transport proteins located in the cytoplasmic membrane are necessary when
A) diffusion will not allow adequate amounts of a substance to enter the cell.
B) movement into the cell is against a concentration gradient.
C) the level of nutrients in nature is very low.
D) nutrient concentration is very low in the environment, transport is needed against the
concentration gradient, or diffusion is not possible.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
7) Cells move polar molecules across the cell membrane against a concentration gradient using
A) energy and transport proteins.
B) simple diffusion.
C) modifications to membrane lipids.
D) random molecular movement.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
8) Bacteria stain as gram-positive or gram-negative because of differences in the cell
A) wall.
B) cytoplasm.
C) nucleus.
D) chromosome.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
2
9) You are given an electron micrograph of a bacterial cell. In the micrograph, you can clearly
see three thin layers of different densities surrounding the cell. Based on the micrograph, you can
infer that this cell is
and would appear
after application of the Gram stain
procedure.
A) gram-positive / purple
B) gram-negative / pink
C) gram-positive / pink
D) gram-negative / purple
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.3
Learning Objective: 2.I
10) The cell wall of a gram-positive bacterium is composed of a thick
A) protein
B) poly-β-hydroxybutyric acid (PHB)
C) lipopolysaccharides (LPS)
D) peptidoglycan
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
layer.
11) You have discovered a new coccoid-shaped microorganism with no nucleus, a rigid cell wall,
and a diameter of 2 μm. Chemical tests reveal that its cell wall does NOT contain peptidoglycan.
The new microorganism is
A) most likely a bacterium.
B) most likely a eukaryote.
C) most likely an archaeon.
D) either a bacterium or an archaeon.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.3
Learning Objective: 2.I
12) The lipopolysaccharide (LPS) layer is found ONLY in the cell walls of
A) gram-positive Bacteria.
B) gram-negative Bacteria.
C) Archaea.
D) Eukarya.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
3
13) An endotoxin is
A) the toxic portion of the LPS.
B) a toxin produced within archaeal cells.
C) a toxin known for its primary attack on the epidermis of mammals.
D) a toxin produced in the periplasm of most bacteria.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
14) Hydrolytic enzymes function in the
A) initial degradation of nutrients.
B) transport of substrates within the cell.
C) chemotactic response, particularly in gram-negative Bacteria.
D) regeneration of the periplasm.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
15) Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli
moving rapidly and randomly through the field of view, changing directions after a brief tumble
and taking off in a different direction. These cells are exhibiting
motility.
A) twitching
B) swimming
C) gliding
D) twitching or gliding
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.9
Learning Objective: 2.III
16) Which of the following statements is FALSE?
A) A flagellar protein subunit is flagellin.
B) In flagellar motion, the basal body acts as a motor.
C) Flagellar rotation generates ATP.
D) The hook is the wider region at the base of the flagellum.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.9
Learning Objective: 2.III
4
17) Which of the following statements is TRUE?
A) Fimbriae are generally longer and less numerous than flagella.
B) Fimbriae are involved in genetic exchange between cells.
C) Hami are common in Bacteria but not found in Archaea.
D) Fimbriae are usually shorter than flagella, whereas pili are involved in genetic exchange.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.6
Learning Objective: 2.II
18) Cellular inclusions in prokaryotic cells serve to
A) store energy rich compounds.
B) protect DNA.
C) position cells in the appropriate environment for survival.
D) store energy rich compounds and position cells in the appropriate environment for survival.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.7
Learning Objective: 2.II
19) A major function of prokaryotic gas vesicles is to
A) confer buoyancy on cells by decreasing their density.
B) serve as a reservoir for oxygen and carbon dioxide.
C) keep the cell's organelles separated during flagellar motion.
D) store oxygen for aerobic growth when oxygen becomes depleted in the environment.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.7
Learning Objective: 2.II
20) The membrane of a gas vesicle is composed of
A) various phospholipids.
B) proteins.
C) carbohydrates.
D) both glycoproteins and phospholipids.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.7
Learning Objective: 2.II
5
21) What is the biological function of endospores?
A) They are bacterial reproductive structures.
B) They enable organisms to endure extremes of temperature, drying, and nutrient depletion.
C) They transport toxins.
D) Endospores can serve as reproductive structures, enable survival in harsh environments, and
transport toxins.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.8
Learning Objective: 2.II
22) The lipids in the cytoplasmic membrane of Bacteria and
contain ester linkages,
while the cytoplasmic membrane of
contain ether linkages.
A) Archaea / Eukarya
B) Archaea / fungi
C) Eukarya / prokaryotes
D) Eukarya / Archaea
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
23) Based on your knowledge of porins from the chapter, what is the best description of the
specific type of porin called an aquaporin?
A) Water transport proteins
B) Molecules that prevent water from crossing a membrane
C) Enzymes involved in the generation of water within cells
D) Cations bound to water molecules
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
24)
are charged molecules that are partially responsible for the _
gram-positive bacterial cell surface.
A) Diaminopimelic acids / positive
B) Teichoic acids / negative
C) Phospholipids / negative
D) Peptide interbridges / neutral
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
6
charge of the
25) Although the inner leaflet of the gram-negative outer membrane is composed mainly of
phospholipids, the outer leaflet of the outer membrane contains
A) pseudopeptidoglycans.
B) lipoteichoic acids.
C) poly-β-hydroxybutyric acids (PHB).
D) lipopolysaccharides (LPS).
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
26) One of the many types of proteins found in the cytoplasmic membrane that is involved in the
chemotactic response is called a
A) hydrolytic enzyme.
B) chemoreceptor.
C) binding protein.
D) porin.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.11
Learning Objective: 2.III
27) When does endospore formation commence?
A) When bacterial growth ceases due to limitation of an essential nutrient
B) When the bacterium is undergoing binary fission
C) When bacteria are dividing exponentially
D) Following bacterial death
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.8
Learning Objective: 2.II
28) Which is/are a function(s) of the cytoplasmic membrane in prokaryotes?
A) It functions as a permeability barrier.
B) It is an anchor for many proteins involved in bioenergetic reactions and transport.
C) It is a major site of energy conservation.
D) It serves as a permeability barrier, a docking station for proteins involved in bioenergetics
reactions and transport, and a site for energy conservation.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
7
29) All eukaryotes contain
A) a membrane-enclosed nucleus.
B) mitochondria.
C) hydrogenosomes.
D) a nucleus, mitochondria, and hydrogenosomes.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.13
Learning Objective: 2.IV
30) Mitochondria and hydrogenosomes are similar in that they both
A) are the site of energy production in eukaryotic cells.
B) evolved via endosymbiosis of bacterial cells.
C) are the site of aerobic respiration.
D) evolved via endosymbiosis and are sites for aerobic respiration and energy production.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.13
Learning Objective: 2.IV
31) Membrane-enclosed organelles, such as nuclei, lysosomes, endoplasmic reticulum,
mitochondria, and chloroplasts
A) form specialized compartments within eukaryotic cells for specific functions to occur.
B) increase the structural complexity of eukaryotic cells.
C) help large eukaryotic cells overcome the limitations of diffusion imposed by their large cell
size.
D) increase structural complexity, help eukaryotes overcome diffusion limitation due to their
size, and form specialized environments for specific functions to occur.
Answer: A
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.13
Learning Objective: 2.IV
32) The Golgi complex functions to
A) modify and secrete proteins to the external environment.
B) sort proteins used within the cell.
C) both modify and sort proteins into those destined for secretion and those that function in
membrane structures.
D) synthesize proteins.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.15
Learning Objective: 2.IV
8
33) The membrane-enclosed compartments that contain digestive enzymes in eukaryotic cells are
called
A) cristae.
B) mitosomes.
C) lysosomes.
D) stromas.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.15
Learning Objective: 2.IV
34) Where within a eukaryotic cell is ribosomal RNA (rRNA) synthesized?
A) Cytoplasm
B) Lysosome
C) Mitochondrion
D) Nucleolus
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.13
Learning Objective: 2.IV
35) The energy source derived from the charge separation across the cytoplasmic membrane is
referred to as
A) the proton motive force.
B) carbohydrate charging.
C) adenosine triphosphate.
D) the voltage source.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
9
36) Based on the table of attributes given below, which of the following statements are FALSE
about the two organisms?
Characteristic
Endospore formation
Capsule
Type IV pili
Flagella
Morphology
Bacterium A
yes
no
yes
no
bacillus
Bacterium B
no
yes
no
no
bacillus
A) Bacterium A is more resistant to heat and ultraviolet light.
B) Bacterium B likely forms a slime layer better than Bacterium A.
C) Bacterium B is likely to exhibit motility.
D) Both bacteria may attach to surfaces.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.5, 2.6, 2.9
Learning Objective: 2.I, 2.II, 2.III
37) Small acid-soluble proteins (SASPs) protect DNA from ultraviolet light and are found in
high numbers within
A) gram-positive Bacteria.
B) endospores.
C) inclusion bodies.
D) gram-negative Bacteria.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.8
Learning Objective: 2.II
38) The peptide interbridge crosslinking between peptidoglycan layers is found ONLY in the cell
walls of
A) Archaea.
B) Eukarya.
C) gram-positive Bacteria.
D) gram-negative Bacteria.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
10
39) Type IV pili are involved in
A) attachment of cells to surfaces.
B) twitching motility.
C) pathogenesis.
D) attachment to surfaces, twitching motility, and pathogenesis.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.6
Learning Objective: 2.II
40) Eukaryotes have
in their cytoplasmic membranes, which serve to strengthen and
stabilize the membrane and make it less flexible.
A) ether bonds
B) lipids
C) sterols
D) phospholipids
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.5
Learning Objective: 2.I
41) The rigid layer that is present in the cell walls of Bacteria that is primarily responsible for the
strength of the wall is known as
A) pseudomurein.
B) S-layer.
C) cellulose.
D) peptidoglycan.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.2
Learning Objective: 2.I
42) Some of the intestinal symptoms elicited by pathogens such as Salmonella, Shigella, and
Escherichia are due to the presence of
A) pseudomurein.
B) S-layers.
C) lipopolysaccharides.
D) peptidoglycan.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
11
43) Using bright-field microscopy to look at a slide prepared with a basic dye you observe cells
with a clear inner compartment within the cell at 400X magnification. The cell is most likely a(n)
A) prokaryote.
B) bacterium.
C) archaeon.
D) eukaryote.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.13
Learning Objective: 2.IV
44) While examining cellular material, you find that organelle DNA is present. What
organelle(s) must be within the sample?
A) Lysosomes
B) Rough or smooth endoplasmic reticulum
C) Chloroplasts or mitochondria
D) Golgi complex
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.14
Learning Objective: 2.IV
45) Which of the following is evidence for the endosymbiotic theory?
A) Mitochondria have circular DNA.
B) The nucleus is surrounded by a nuclear membrane.
C) Chloroplasts have thylakoids.
D) The rough endoplasmic reticulum has ribosomes.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.14
Learning Objective: 2.IV
46) Actin is found within
A) the prokaryotic cytoskeleton.
B) eukaryotic microfilaments.
C) eukaryotic microtubules.
D) eukaryotic intermediate filaments.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.15
Learning Objective: 2.IV
12
47) Which of the following statements is TRUE?
A) Eukaryotic flagella rotate in the same manner as prokaryotic flagella.
B) Lysosomes synthesize proteins and carbohydrates.
C) Cilia generally move with a slow, whip-like motion.
D) The major function of the rough endoplasmic reticulum is lipid synthesis.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.15
Learning Objective: 2.IV
48) Archaeans have archaella that rotate like bacterial flagella though they
A) have greater diameters than bacterial flagella.
B) are longer than bacterial flagella.
C) only rotate in one direction.
D) consist of multiple protein types.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.9
Learning Objective: 2.III
49) You find endospores of a particular species. Which of the following is most likely TRUE of
this species?
A) It is an archaean.
B) It is a gram-positive bacterium.
C) It is a gram-negative bacterium.
D) It is equally likely to be an archaean, a gram-positive bacterium, or a gram-negative
bacterium.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.8
Learning Objective: 2.II
50) The disease anthrax is caused by the pathogenic bacterium
resistant structures known as
.
A) Azotobacter chroococcum / endospores
B) Azotobacter chroococcum / plasmids
C) Bacillus anthracis / endospores
D) Bacillus anthracis / plasmids
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.8
Learning Objective: 2.II
13
, which produces heat-
2.2 True/False Questions
1) In general, most cell inclusions function as energy reserves or as a reservoir of structural
building blocks.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.7
Learning Objective: 2.II
2) In general, lipids in archaeal cytoplasmic membranes lack true fatty acids.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
3) Some membrane proteins are involved in bioenergetic reactions, while others are involved in
membrane transport.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.2
Learning Objective: 2.I
4) Both hydrophilic and charged molecules readily diffuse through the cytoplasmic membrane.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
5) Teichoic acids are commonly found in gram-negative cell walls.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
6) Despite the invariance of the backbone of peptidoglycan, there are more than 100 different
types of peptidoglycan.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.3
Learning Objective: 2.I
7) Lysozyme is an enzyme that can ultimately lyse and kill eukaryotic cells by breaking β-1, 4glycosidic bonds in peptidoglycan.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.3
Learning Objective: 2.I
14
8) Porins are channels in the outer membranes of gram-positive Bacteria.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.4
Learning Objective: 2.I
9) In general, swimming is performed with flagella, whereas gliding uses other cellular
components such as pili.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.6
Learning Objective: 2.II
10) Chemotaxis is a sensory response affecting the rotational direction of the flagellar motor.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.11
Learning Objective: 2.III
11) Photoreceptors are analogous to chemoreceptors in that they are both proteinaceous sensors.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.12
Learning Objective: 2.III
12) Pathogenic bacteria that contain S-layers are protected against host defense mechanisms.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.5
Learning Objective: 2.I
13) Poly-β-hydroxybutyric acid (PHB) is a carbon- and energy-storing polymer.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.7
Learning Objective: 2.II
14) Mitochondria and chloroplasts have their own DNA and ribosomes, which supports the
endosymbiotic hypothesis.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.14
Learning Objective: 2.IV
15
15) Macromolecules resulting from lysosomal digestion are used in cellular biosynthesis and
energy generation.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.15
Learning Objective: 2.IV
16) ATP-binding cassette transport systems have high substrate affinity and thus help
microorganisms survive in low nutrient environments.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.2
Learning Objective: 2.I
2.3 Essay Questions
1) Describe the makeup of the phospholipid bilayer. Include molecular orientation and proteins
as well.
Answer: The fatty acid components of the lipids in the cytoplasmic membrane are oriented
toward each other, whereas the glycerol-phosphates point out toward the cytoplasm and external
environment. Proteins can span the entire membrane (both layers) or be embedded in the
phospholipids on either side of the membrane.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
2) Compare and contrast the chemical composition and structure of the cytoplasmic membranes
found in Bacteria and Archaea. What is the advantage of the archaeal membranes in relationship
to the types of environments archaea may inhabit?
Answer: Bacterial cytoplasmic membranes contain fatty acids with ester linkages that always
form a phospholipid bilayer that is highly fluid. Archaeal cytoplasmic membranes contain
glycerol ethers that are either diether or tetraethers. Glycerol diether molecules form a bilayer
membrane and glycerol tetraether form a monolayer membrane. Both the ether linkages and the
monolayer structure are more rigid than the bilayer ester-linked fatty acids and are more stable at
high temperatures and pressures. Archaea tend to inhabit more extreme environments in terms of
temperature, pressure, and salt, thus the more stable membrane components allow archaea to
survive under these conditions.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.1
Learning Objective: 2.I
16
3) You are studying swimming motility in a pathogenic bacillus. You create mutations in random
genes and then test which mutations effect swimming motility by looking at the mutant cells
under the microscope. One of the mutant bacteria cannot swim anymore, but still rotates around
in one spot when you watch them. Using electron microscopy, you discover that some parts of
the flagella are still present in the cell wall, but no long flagella are visible. Which gene do you
think is mutated (i.e., missing) and which motility-related parts are still present in this mutant?
Answer: The flagellar apparatus is put together in a particular order, first the MS ring, anchoring
proteins, and the hook extend off of the cytoplasmic membrane. Flagellin proteins then pass
through the narrow filament channel and cap proteins finally are put onto the end when roughly
20,000 flagellin have been assembled. Flagellar growth thus occurs after the assembly of the
basal body, rings, and hook. The basal body provides the rotation and uses the proton motive
force to rotate the basal body. From the information given above, one can infer that the basal
body and hook can still rotate, but the flagellin proteins are missing or defective so that no long
flagella can form. This would explain why the cells might still rotate in place, but not be able to
move forward rapidly.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.9
Learning Objective: 2.III
4) Describe the mechanisms by which certain prokaryotes glide. What are the ecological
advantages of gliding motility?
Answer: Mechanisms will vary depending on the organism described, some of which include
the involvement of proteins in the cytoplasmic membrane, slime extrusion, and type IV pili.
Examples of advantages could include biofilm formation on a surface, increased pathogenesis or
movement toward a different habitat with new resources.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.10
Learning Objective: 2.III
5) What is the function of an endospore and how is an endospore formed?
Answer: The function of an endospore is to allow the cell to survive harsh conditions by going
into a dormant state. An environmental trigger, such as nutrient depletion or dehydration triggers
the formation of compounds such as SASP and dipicolinic acid to protect the DNA from damage
and reduce the water content inside the endospore. These changes protect the DNA and other
critical chemical components from heat, desiccation, and UV exposure. The function of an
endospore is not for reproduction because every cell forms only one endospore. (The amount of
detail expected in this answer should commensurate with the amount of detail discussed in
class.)
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.8
Learning Objective: 2.II
17
6) You have discovered a new bacterial strain that causes urinary tract infections. Closely related
bacterial species cannot cause infections. You compare the strains and find that your new strain
has structures composed of protein external to its cell wall. What structures might your new
strain have that the other strains do not? Why?
Answer: Pili or fimbriae are the most likely structures that are found in the new pathogenic
strain but missing in the nonpathogenic strains. Both pili and fimbriae aid in attachment of cells
to surfaces and tissues. Attachment is important for pathogenesis. In addition, some pili are
involved in twitching motility, which can help cells invade the body. (Other answers such as the
capsule would only be partly correct, since the capsule is not made of protein. Flagella could also
be an acceptable answer if they logically connect swimming motility to pathogenesis.)
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.6
Learning Objective: 2.II
7) Construct a chart to show at least five major differences between the cytoplasmic membrane
and cell wall of bacteria and archaea. What are the implications of these differences?
Answer: Answers could include the following: the abundance or presence of amino acid
stereoisomers, polysaccharides, pseudomurein and S-layers, action of lysozyme and penicillin,
and type of glycosidic bonds.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.1, 2.3
Learning Objective: 2.I
8) Elaborate on why discovering endospores was important to microbiology.
Answer: Endospores allow bacteria to survive boiling water, UV light, and extreme desiccation,
as well as allowing them to be in a dormant state for very long periods of time. Two possible
themes could be how the discovery of endospores changed sterilization procedures for food and
surgical instruments, as well as a change in our view of how bacteria can survive, such as
surviving in space and surviving 1,000s of years in a dormant state.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.8
Learning Objective: 2.II
9) Predict what would happen to a motile bacterium undergoing chemotaxis if the Mot proteins
suddenly ceased to function.
Answer: The function of Mot proteins should be described producing the rotation of the flagella.
This would probably allow flagella to form, but they would not be able to rotate. The bacterium
would not be able to move, but the flagella would still look normal.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.9
Learning Objective: 2.III
18
10) Explain why a eukaryotic cell needs membrane-enclosed lysosomes and peroxisomes.
Answer: The structures both contain high concentrations of enzymes that serve as a localized
region to perform specific reactions. Enclosed membranes provide a barrier to maintain
conditions within the lysosomes and peroxisomes that are unlike those in the cytoplasm, which is
important because environmental conditions for these processes to be optimal are often different
than the conditions in the cytoplasm.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.15
Learning Objective: 2.IV
11) Antibiotics such as penicillin interfere with the ability of bacteria to synthesize cell walls.
Explain why cell walls are a good target for a useful antibiotic and whether you think that
penicillin would be effective against a bacterial cell in an isotonic environment.
Answer: Because human cells do not use peptidoglycan, an antibiotic that affects peptidoglycan
can harm bacterial cells with less risk of damage to human cells even though all medications may
have some adverse effects (such as causing an allergic reaction). In an isotonic environment, a
bacterial cell can survive without a cell wall and therefore penicillin would be less effective than
in a hypotonic environment.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 2.3
Learning Objective: 2.I
12) How would the presence of endospores in Louis Pasteur's nutrient solutions have affected his
conclusions about spontaneous generation?
Answer: Answers will vary, but ultimately this could have confounded Pasteur if the endospores
sometimes went into a vegetative growth phase and other times no growth was observed.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 2.8
Learning Objective: 2.II
13) Explain the differences between symporters and antiporters.
Answer: Answers should highlight differences in transport direction and energy input.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 2.1
Learning Objective: 2.I
19
Brock Biology of Microorganisms, 16e (Madigan et al.)
Chapter 4 Microbial Growth and Its Control
4.1 Multiple Choice Questions
1) Bacterial growth refers to
A) an increase in the number of cells.
B) the occurrence of binary fission.
C) the time required for one cell to divide into two.
D) the occurrence of mitosis.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.1
Learning Objective: 4.I
2) The time interval required for the formation of two cells from one is called the
A) generation time.
B) growth time.
C) growth rate.
D) division rate.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.6
Learning Objective: 4.II
3) Turbidity measurements are commonly utilized for monitoring
A) planktonic cultures.
B) biofilms.
C) conies.
D) sessile cultures.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.5
Learning Objective: 4.I
4) The time between inoculation and the beginning of growth is usually called the
A) lag phase.
B) log phase.
C) dormant phase.
D) decline phase.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.6
Learning Objective: 4.II
1
5) Optical density and viable cell concentration are LEAST proportional to each other during the
A) lag phase.
B) exponential growth phase.
C) stationary phase.
D) decline phase.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
6) When attempting to determine viable cell counts of a heat-sensitive bacterial isolate, which
cell counting method should be avoided?
A) Spread-plate method
B) Pour-plate method
C) Live staining and direct counting with a microscope
D) Both spread- and pour-plate methods
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
7) Bacteria that are able to grow in humans and cause disease would be classified as
A) psychrophiles.
B) mesophiles.
C) thermophiles.
D) hyperthermophiles.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.11
Learning Objective: 4.III
8) An agar plate for counting colonies and maximizing statistical validity should ideally contain
A) 1 to 100 colonies.
B) 50 to 100 colonies.
C) 30 to 300 colonies.
D) 100 to 1000 colonies.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.4
Learning Objective: 4.I
2
9) Relative to enzymes in mesophilic microorganisms, which of the following is NOT
characteristic of enzymes in psychrophiles?
A) Decreased alpha helix content
B) Decreased beta sheet content
C) Fewer hydrogen bonds
D) Fewer ionic bonds
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.12
Learning Objective: 4.III
10) The number of colonies obtained in a plate count does NOT depend on the
A) inoculum volume.
B) size of the colonies.
C) type of culture medium.
D) incubation time.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
11) Cell density in a chemostat is controlled by
A) the concentration of the limiting nutrient.
B) the dilution factor.
C) the size of the initial inoculum.
D) the concentration of the limiting nutrient, the dilution factor, and the size of the initial
inoculum.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.8
Learning Objective: 4.II
12) What temperature is most commonly used in autoclaves to sterilize growth media and other
devices prior to experimentation?
A) 95°C
B) 101°C
C) 121°C
D) 140°C
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.17
Learning Objective: 4.V
3
13) Most mesophilic organisms can grow in a temperature range of
A) 0-15°C.
B) 10-20°C.
C) 20-45°C.
D) 50-65°C.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.11
Learning Objective: 4.III
14) Obligate anaerobes which are sensitive to O2 would be found growing
A) throughout a tube of thioglycolate broth.
B) only at the very top of a tube of thioglycolate broth.
C) only at the bottom of a tube of thioglycolate broth.
D) approximately one-third of the way down the thioglycolate broth.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.16
Learning Objective: 4.IV
15) A microbe growing in a refrigerator is likely
A) psychrophilic.
B) mesophilic.
C) psychrotolerant or psychrophilic.
D) hyperthermophilic.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.12
Learning Objective: 4.III
16) Which of these statements is/are TRUE?
A) In general, species that can grow at higher temperatures are prokaryotic.
B) The most thermophilic prokaryotes are species of Archaea.
C) Chemoorganotrophic organisms are able to grow at higher temperatures than phototrophic
organisms.
D) All of the statements are true.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
4
17) A chemical that denatures proteins is most likely to be classified as a(n)
A) antiseptic
B) bacteriostatic
C) bactericidal
D) detergent
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.19
Learning Objective: 4.V
agent.
18) The ratio of the vapor pressure of the air in equilibrium with a substance to the vapor
pressure of pure water is known as
A) water activity.
B) vapor activity.
C) positive water balance.
D) osmosis.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.15
Learning Objective: 4.IV
19) Organisms able to live in environments with high sugar concentrations are
A) halotolerant.
B) osmophiles.
C) xerophiles.
D) anaerobic fermenting bacteria.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.15
Learning Objective: 4.IV
20) When water activity is low, an organism must
A) increase its internal solute concentration.
B) increase its external solute concentration.
C) decrease its internal solute concentration.
D) decrease its external solute concentration.
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.15
Learning Objective: 4.IV
5
21) A bacterium possessing
will produce O2 bubbles when placed in the presence of
hydrogen peroxide.
A) catalase
B) superoxide dismutase
C) superoxide reductase
D) peroxidase
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.16
Learning Objective: 4.IV
22) A halotolerant facultative anaerobe would grow BEST in which of the following
environments?
A) Oxygen depleted saline
B) Oxygenated saline
C) Oxygen depleted non-saline
D) Oxygenated non-saline
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.15/4.16
Learning Objective: 4.IV
23) Which of the following forms of oxygen is/are generally toxic to living organisms?
A) Superoxide anion
B) Hydrogen peroxide
C) Hydroxyl radical
D) Superoxide, hydrogen peroxide, and hydroxyl radicals are all toxic.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.16
Learning Objective: 4.IV
24) Superoxide dismutase and catalase work together to convert superoxide into
A) peroxide.
B) oxygen.
C) water.
D) water and oxygen.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.16
Learning Objective: 4.IV
6
25) Which of the following methods used to enumerate cells often requires specialized staining
to observe nonpigmented bacteria?
A) Spectrophotometry/turbidity
B) Spread-plating
C) Microscopy
D) Spread-plating, turbidity, and microscopy
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.3
Learning Objective: 4.I
26) Which term is most relevant in describing the efficacy of an antimicrobial for use in a
clinical setting?
A) Effective dose
B) Sterilization coefficient
C) Lethal dosage
D) Minimum inhibitory concentration (MIC)
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.19
Learning Objective: 4.V
27) Which method would be LEAST effective at sterilizing a glass hockey stick to use in the
spread-plate method?
A) Autoclaving
B) Gamma radiation
C) Ethanol soaking
D) Ultrahigh-temperature pasteurization
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.18
Learning Objective: 4.V
28) When counting colonies on an agar plate
A) it is assumed that each colony arose from division of one or a few cells.
B) only viable colonies are counted.
C) the medium must be suitable for colony growth.
D) All of these answer choices are true.
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
7
29) By controlling the concentration of nutrients continuously added to a chemostat, cells can
constantly be maintained at the
A) exponential growth phase.
B) stationary growth phase.
C) lag growth phase.
D) death growth phase.
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.8
Learning Objective: 4.II
30) Serial dilutions are generally made
A) when the appropriate viable count is unknown.
B) based on powers of 10, although other serial dilution factors are possible.
C) to reach a suitable dilution while minimizing error.
D) All of these answer choices apply.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
31) Which of the following statements is FALSE?
A) In the death phase, bacterial growth may cease as a result of oxygen and nutrient depletion.
B) The generation time of bacteria may vary from species to species.
C) Bacteria typically divide by binary fission, producing two daughter cells.
D) In the lag phase, cell death exceeds cell division.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.6
Learning Objective: 4.II
32) The optimal growth temperature of a bacterium is most closely related to the optimal
temperature for
A) transcription of DNA.
B) DNA replication.
C) enzyme function.
D) mRNA attachment to ribosomes.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.11
Learning Objective: 4.III
8
33) Why is the enzyme catalase important to the survival of bacteria?
A) Catalase protects the cell from desiccation.
B) Catalase breaks down toxic hydrogen peroxide.
C) Catalase allows for growth in high salt concentrations.
D) Catalase aids in the transport of oxygen into the cell.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.16
Learning Objective: 4.IV
34) A medium containing known substances in precise amounts is known as a
A) selective
B) complex
C) natural
D) defined
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.2
Learning Objective: 4.I
media.
35) Selective medium differs from differential medium because
A) selective medium permits growth of more organisms than differential medium.
B) selective medium permits growth of a particular microbial type while differential medium is
used to distinguish between types of organisms.
C) differential medium differentiates pathogens from nonpathogens while selective medium
grows only pathogens.
D) differential medium contains growth inhibitors while selective medium does not.
Answer: B
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.2
Learning Objective: 4.I
36) The cell membranes of thermophiles and hyperthermophilic bacteria typically have
A) more saturated fatty acids.
B) more long chain fatty acids.
C) fewer unsaturated fatty acids.
D) All of these answer choices are true of thermophiles and hyperthermophilic bacteria.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
9
37) The use of chemical agents directly on exposed body surfaces to destroy or inhibit vegetative
pathogens is
A) disinfection.
B) sterilization.
C) antisepsis.
D) sanitization.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.19
Learning Objective: 4.V
38) Which of the following statements is TRUE of disinfectants?
A) They are always effective in destroying endospores.
B) They are used on living tissue.
C) They are used for sterilization.
D) They are used on inanimate surfaces.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.19
Learning Objective: 4.V
39) A
agent is a chemical that inhibits bacteria from reproducing, but does NOT
necessarily kill them.
A) bacteriostatic
B) bacteriolytic
C) bacteriocidal
D) xerophilic
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.19
Learning Objective: 4.V
40) Microbial contamination is prevented by the
A) use of the quadrant streak method.
B) use of aseptic technique.
C) use of cultures containing special nutrients.
D) spread-plate method.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.2
Learning Objective: 4.I
10
41) A common antimicrobial chemical (or chemicals) used as both an antiseptic and a general
disinfectant is
A) iodophors.
B) 70% alcohol.
C) hydrogen peroxide.
D) Each of the above chemicals at appropriate concentrations can be used as antiseptics or
disinfectants.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.19
Learning Objective: 4.V
42) Cultures of a bacterial species were incubated on the shelf of a refrigerator (5°C), on a lab
benchtop (25°C), on the shelf of a 37°C incubator, and on the shelf of a 50°C incubator. After
incubation, there was no growth at 37°C or 50°C, slight growth on the benchtop, and abundant
growth at refrigeration. What term could be used for this species?
A) Halophile
B) Mesophile
C) Anaerobe
D) Psychrophile
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.11
Learning Objective: 4.III
43) A microbiology student in a research lab repeated an experiment described by others using
the identical bacterial isolate, the same growth medium, and the same growth conditions.
However, the student was unable to achieve the same O.D. at 600 nm. What is the LEAST likely
cause for this discrepancy in measured turbidity?
A) One experiment used 16 mm wide test tubes while the other used 18 mm wide test tubes.
B) One experiment subtracted the yellow color of the growth medium away from the final
turbidity reported whereas the other used colorless water.
C) One experiment vigorously dispersed the bacterial pellicle with vortexing while the other did
not.
D) The two experiments were carried out at vastly different elevations and did not consider the
influence of pressure.
Answer: D
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.5
Learning Objective: 4.I
11
44) Which is an example of a micronutrient?
A) Arginine
B) Inorganic phosphorous
C) Iron
D) Vitamin B12
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.1
Learning Objective: 4.I
45) To ensure growth of a newly discovered bacterium with unknown nutritional requirements, it
would be best to begin with a
medium rather than a
medium.
A) complex / minimal
B) minimal / complex
C) selective / complex
D) selective / differential
Answer: A
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.2
Learning Objective: 4.I
46) Which element functions BOTH as an enzyme cofactor and as a stabilizer of ribosomes and
nucleic acids?
A) Iron
B) Hydrogen
C) Zinc
D) Magnesium
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.1
Learning Objective: 4.I
47) All microorganisms require
A) carbon, iron, and sodium.
B) phosphorus, aluminum, and sodium.
C) calcium, potassium, and magnesium.
D) phosphorus, nitrogen, and sulfur.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.1
Learning Objective: 4.I
12
4.2 True/False Questions
1) Microbial growth is generally described as an increase in cell number rather than the
expansion in size of an individual microbial cell.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.1
Learning Objective: 4.I
2) The duration of exponential growth would increase if bacterial cells divided into three equal
daughter cells rather than two.
Answer: FALSE
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.6
Learning Objective: 4.II
3) A selective medium is used to suppress the growth of some bacteria in order to facilitate the
growth of other bacteria.
Answer: TRUE
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.2
Learning Objective: 4.I
4) The lag phase does NOT occur if an exponentially growing culture is transferred into a
nutrient rich medium with the same components and growth conditions as the previous medium.
Answer: TRUE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
5) The rate of exponential growth varies greatly according to bacterial species and bioavailable
nutrients.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.6
Learning Objective: 4.II
6) A bacterium whose optimal growth temperature is 35˚C would be classified as a thermophile.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.11
Learning Objective: 4.III
13
7) A complex medium is one that has been completely made in the laboratory and the
concentration of all the nutrients is known.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.2
Learning Objective: 4.I
8) Many fungi and bacteria grow best at pH 5 or below.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.14
Learning Objective: 4.IV
9) In both the lag and stationary phase, there is no net increase or decrease in viable cells.
Answer: TRUE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
10) The death phase applies to individual cells rather than populations.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.6
Learning Objective: 4.II
11) Direct microscopic counting of cells is an accurate method for estimating the number of
viable cells in a sample.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.3
Learning Objective: 4.I
12) The optimal pH for growth of an organism refers to its intracellular environment.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.14
Learning Objective: 4.IV
13) When viable cell concentrations are too high to count on an agar plate, it is common to use
larger sized plates to increase the surface area for counting the colonies.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
14
14) Refrigeration controls microbial growth in food as a result of irreversible cell damage caused
by low temperature.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.7
Learning Objective: 4.II
15) The optimum growth temperature for an organism is typically closer to its minimum
temperature rather than the maximum temperature.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.11
Learning Objective: 4.III
16) A bacterium such as a snow alga that is able to grow in cold temperatures is called a
psychrophile.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.12
Learning Objective: 4.III
17) Some microbes can grow in boiling water.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
18) Organisms living in boiling hot springs often grow rapidly and have short doubling times.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
19) Taq polymerase was isolated from a thermophile and is used in the polymerase chain
reaction (PCR) technique because it does not become inactivated at high temperatures.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
20) Mesophiles typically have longer fatty acid tails and more saturated carbon-carbon bonds in
their cytoplasmic tails compared with thermophiles.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.13
Learning Objective: 4.III
15
21) Knowledge of microbial growth patterns is useful in working with the control of microbial
growth.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.17
Learning Objective: 4.V
22) Irreversible cell damage is more likely to occur at low rather than high temperatures.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
23) Based on studies with obligate acidophiles, high concentrations of hydrogen ions are
required for their membrane stability.
Answer: TRUE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.14
Learning Objective: 4.IV
24) A bacterial cell in nutrient broth with a generation time of 15 minutes will produce 16 cells
in 2 hours.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
25) Planktonic cells remain in suspension while sessile cells adhere to a surface.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.9
Learning Objective: 4.II
26) The thermal death time is the time needed to kill all the bacteria in a particular culture at a
certain temperature.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.17
Learning Objective: 4.V
27) Autoclaving and pasteurization are two processes that are both very effective for
sterilization.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.17
Learning Objective: 4.V
16
28) Most microorganisms are particularly susceptible to antimicrobial agents during the
logarithmic growth phase.
Answer: TRUE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.19
Learning Objective: 4.V
29) Sterility of a laminar flow hood is accomplished by filter-sterilized air passed through the
hood quickly enough that nonsterile air does not flow into the work area.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.18
Learning Objective: 4.V
4.3 Essay Questions
1) Use the formulas N = N02n and g = t/n.
N = final cell number, N0 = initial cell number,
n = number of generations, t = time, g = generation time.
Find the generation time if N = 2 × 108, N0 = 3 × 106, and t = 3 hours.
Answer: The number of generations (n) must first be determined through the rearranged
formula: n = [(log N)-(log N0)]/(log 2) to determine n = 6.059 generations. Finally, the
generation time (g) = t/n, which equates to nearly 0.5 hour per generation or almost 30 minutes
per generation.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
2) Explain the difference between the division rate and the generation time.
Answer: Generation time (g) and division rate (v) are reciprocal values of each other; both are
determined by monitoring exponential growth over time. Division rate is reported as the number
of generations per time and is calculated by taking 1/g. The units for g are in time per generation,
which is the doubling time during exponential growth.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.6
Learning Objective: 4.II
17
3) Knowing the concentration of microorganisms in a sample is often an important consideration
for environmental, industrial, and medical microbiologists, yet a microscope is sometimes not
used to accomplish this task. Explain five major limitations to using a light microscope to
directly count microorganisms.
Answer: All of the following eight are potential issues associated with the direct counting
method: (1) live and dead cells are indistinguishable without special staining, (2) low cell
concentrations are challenging to enumerate, (3) motile cells must be immobilized, (4) precision
can be quite poor with manually counting hundreds or thousands of cells, (5) small cells are
difficult to observe and count even at 1,000X total magnification, (6) small particulates can be
mistaken for microbial cells, (7) unstained cells require more sophisticated microscopy, and (8) it
is very time-consuming.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.3
Learning Objective: 4.I
4) Compare and contrast the spread-plate method and the pour-plate method of doing plate
counts. Also, describe which group of organisms would not be quantifiable in the pour-plate
method but would still be observed in the spread-plate method.
Answer: Answers will vary, but one benefit to the pour-plate method is that larger volumes of
cells can be dispensed, whereas large liquid volumes dispensed on the surface of agar plates is
often impractical. Many cells, especially psychrophiles and some mesophiles, cannot withstand
the warm temperature of molten agar (~50°C) and therefore must be spread on top of an agar
plate. Colonies are easier to enumerate on a two- rather than three-dimensional surface that
favors the spread-plate technique over the pour plate method.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.4
Learning Objective: 4.I
18
5) Enumerating the viable and total cell concentration of a population of a microbial isolate can
be a laborious task for a microbiologist, especially when studying the same isolate for several
years. It is often more practical to determine the relationship between optical density (OD) and
cell concentration. Once this relationship (determined by a standard curve) is determined, the OD
of an isolate in a broth can be used to determine the population's concentration. Why must a
standard curve be prepared for each isolate when using OD measurements to determine cell
concentration? Also, describe an experiment that would generate this type of standard curve.
Answer: Answers will vary, but it should be noted that a particular OD value will correspond to
a specific cell concentration due to different shapes and sizes of microorganisms. One such
example could be a culture of Citricella sp. SE45, which was determined to have an OD540 of
0.485. This OD fit into the already-constructed standard curve to indicate that 5 × 105 viable
cells are in each milliliter of broth, which can be helpful in experiments where the final cell
concentration or number is critical. To initially create the standard curve, a traditional growth
curve experiment could be performed over time where both OD and cell concentration (viable
with viability plating or total with direct counts) would be measured. The values of OD and cell
concentration for each time point would then be used to create a standard curve, and a linear
regression curve would show the relationship of OD to cell concentration such that subsequent
experiments OD could be measured as a proxy for cell concentration.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.5
Learning Objective: 4.I
6) Explain why a hyperthermophile is unlikely to be a human pathogen.
Answer: The human body's temperature is approximately 37°C, which is not a favorable
environment for a hyperthermophile, which has an optimal growth temperature of 80°C or
higher.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
7) Explain the present understanding of molecular adaptations to the cytoplasmic membrane as
found in psychrophiles.
Answer: Nonpsychrophiles do not thrive in the cold environment, in part due to predominantly
having large or saturated fatty acid chains in their cytoplasmic membrane, which become
increasingly rigid and wax-like with colder temperatures. The psychrophiles have higher relative
concentrations of short and unsaturated fatty acids in their membrane and therefore maintain a
semi-permeable membrane when exposed to less heat.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.12
Learning Objective: 4.III
19
8) Explain the present understanding of molecular adaptations to the cytoplasmic membrane that
are present in thermophiles.
Answer: In thermophiles and most hyperthermophilic Bacteria, the cytoplasmic membrane has a
higher content of long-chain and saturated fatty acids and a lower content of unsaturated fatty
acids than are found in the cytoplasmic membranes of mesophiles. Saturated fatty acids form a
stronger hydrophobic environment than do unsaturated fatty acids, and longer-chain fatty acids
have a higher melting point than shorter-chain fatty acids; collectively these properties increase
membrane stability.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.13
Learning Objective: 4.III
9) Would you expect a xerophilic organism to be halotolerant? Why or why not?
Answer: Yes, xerophiles are typically halotolerant. For example, the xerophilic halotolerant
fungus Xeromyces bisporus inhabits cereal, candy, and dried fruit, all of which are very dry
environments that also contain salt. With all else being equal, a decrease in solvent (such as
water) translates to an increase in solute (salt) concentration, and therefore a microbe capable of
tolerating a low water activity likely can also tolerate higher salt concentrations.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.15
Learning Objective: 4.IV
10) Describe the autoclave, and explain the roles of time, temperature, and pressure in the
functioning of the autoclave.
Answer: High pressure is used in an autoclave so that liquids do not boil at temperatures beyond
100°C. The heat (not pressure) is used to kill living cells and is usually used for 15 minutes at
121°C. The time must be increased for bulky samples to ensure the objects or liquids are heated
to 121°C for at least 15 minutes.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 4.17
Learning Objective: 4.V
11) Discuss the pros and cons of using radiation to sterilize items such as foods, drugs, and
surgical supplies.
Answer: UV radiation sterilizes only the surfaces of objects which can be problematic for foods
that are not fully cooked on the inside. Ionizing radiation can penetrate so they are ideal for foods
such as grain cereals and ground beef. The high costs associated with the specialized equipment
make it feasible only for large industrial applications. Due to the high energy of some of these
radiation procedures, there are many concerns of potential radioactive contamination, production
of carcinogenic or toxic products, and nutritional value alteration.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.18
Learning Objective: 4.V
20
12) Why is 100% ethanol less effective as an antimicrobial compared to a 70-95% concentration
of ethanol?
Answer: Seventy percent alcohol is ideal as opposed to a stronger solution. Pure alcohol
coagulates protein on contact. If 100% alcohol is poured over a single-celled organism, the
alcohol goes through the cell wall of the organism in all direction and coagulates the proteins
found in the cell membrane. The coagulated membrane proteins would then stop the alcohol
from penetrating further into the cell, preventing denaturation of cytoplasmic proteins. If this
happened, the cell would become inactive but not dead. Under favorable conditions, the cell
would then begin to function. If 70% alcohol is poured over a single celled organism, the diluted
alcohol also coagulates the protein, but at a slower rate, so that it is able to penetrate all the way
through the cell before protein coagulation can block it. Thus, the protein found in the entire cell
is coagulated and the organism dies.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 4.19
Learning Objective: 4.V
13) Why are microbial doubling times in nature typically longer than those obtained in the
laboratory?
Answer: The general theme should be on how lab conditions are designed to optimally grow a
microorganism (e.g., pH, substrate(s), temperature, vitamins) and minimize pressure. In the
environment, this microbe often is in conditions that are less than ideal, where they likely will
encounter competition for growth substrates and other essential chemicals.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 4.2
Learning Objective: 4.I
21
Brock Biology of Microorganisms, 16e (Madigan et al.)
Chapter 7 Microbial Regulatory Systems
7.1 Multiple Choice Questions
1) Regulation of enzyme activity occurs
A) at the start of transcription.
B) at the start of translation.
C) posttranslationally.
D) at any point on the enzymatic production pathway.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.16
Learning Objective: 7.V
2) When arginine is added to a culture already growing exponentially in a medium without
arginine, what occurs?
A) All cellular growth ceases.
B) Growth continues, but the production of enzymes required for the synthesis of arginine
ceases.
C) Growth continues, but the production of enzymes required for the synthesis of arginine
increases.
D) The cell returns to the lag stage of growth to synthesize the proteins necessary for the
metabolism of arginine.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.3
Learning Objective: 7.I
3) Regulatory proteins
A) are influenced by small molecules.
B) bind to specific DNA sites.
C) regulate transcription.
D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
1
4) A protein region with a specific function and structure is called a
A) conserved site.
B) domain.
C) locale.
D) motif.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
5) Transcriptional regulators bind most frequently at the
A) major groove
B) minor groove
C) histone complex
D) primary supercoil
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
site of DNA.
6) Which type of regulator(s) specifically binds to operator regions of DNA?
A) Activators
B) Activators and inducers
C) Repressors
D) Repressors and corepressors
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
7) The lac operon is an example of
control in which the presence of an
required for transcription to occur.
A) negative / activator
B) negative / inducer
C) positive / activator
D) positive / inducer
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
2
is
8) Enzyme induction occurs
A) when the substrate is present.
B) when the organism is environmentally stressed.
C) continuously.
D) when the substrate is depleted.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
9) Considering the catabolite repression mechanism, which observation would make you suspect
it IS occurring?
A) CRP bound to promoter sites
B) Elevated levels of transcripts for maltose and sucrose catabolism
C) Relatively low intracellular cyclic AMP levels
D) RNA polymerase bound to biosynthetic promoter sequences
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.8
Learning Objective: 7.III
10) During a growth curve of Aliivibrio fischeri, when would you expect to see the strongest
bioluminescence?
A) Lag phase
B) Early to middle log phase
C) Late log to early stationary phase
D) Middle to late stationary phase
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.7
Learning Objective: 7.II
11) What occurs when an inducer is added to an environment containing an organism with a
metabolic pathway controlled by a repressor?
A) The inducer combines with the repressor and activates the pathway.
B) The inducer combines with the repressor and inactivates the pathway.
C) The inducer combines with the substrate and blocks induction.
D) The inducer does not combine with, but functions as a chaperone molecule for, the enzymesubstrate complex.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.2, 7.3
Learning Objective: 7.I
3
12) Which of the following do NOT bind to the promoter sequence during regulation?
A) Activators
B) Inducers
C) Repressors
D) None of these bind directly to the promoter sequence.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
13) Cyclic AMP is synthesized from ATP by an enzyme called
.
A) adenylate cyclase / catabolite repression
B) adenylate cyclase / transcriptional activation
C) cAMP receptor protein (CRP) synthase / catabolite repression
D) cAMP receptor protein (CRP) synthase / transcriptional activation
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.8
Learning Objective: 7.III
which is involved in
14) In negative control of transcription by the lac operon, how does the presence of an inducer
affect transcription?
A) The inducer binds to the operator.
B) The inducer does not bind to the operator.
C) The inducer causes the repressor to bind to the operator.
D) The inducer prevents the repressor from binding to the operator.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.8
Learning Objective: 7.III
15) Mechanisms for controlling enzyme activity include all of the following EXCEPT
A) degradation of the enzyme.
B) feedback inhibition.
C) covalent modification of the enzyme.
D) addition of short sections of new amino acid sequence.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
4
16) The function of a kinase is
A) methylation.
B) response regulation.
C) phosphorylation.
D) glycosylation.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.5
Learning Objective: 7.II
17) The promoters of positively controlled operons require activator proteins because
A) RNA polymerase easily recognizes the consensus sequence.
B) they are required to inactivate the repressor proteins.
C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA
polymerase recognize the promoter.
D) they are needed to bind to the allosteric site of RNA polymerase.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
18) Transcriptional control in Archaea most closely resembles that in
.
A) bacteria / regulatory proteins
B) eukaryotes / regulatory proteins
C) bacteria / transcription factors
D) eukaryotes / transcription factors
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
and utilizes
19) The most frequent way in which small regulatory RNA molecules exert their effects is by
A) base pairing with other RNA molecules that have regions of complementary sequence.
B) binding to a repressor and repressing enzyme transcription.
C) acting as an inducer that then binds to an activator protein to allow transcription to proceed.
D) signal transduction.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.12
Learning Objective: 7.IV
5
20)
pathways typically rely on
_ proteins to inhibit mRNA synthesis.
A) Anabolic / repressor
B) Catabolic / repressor
C) Anabolic / activator
D) Catabolic /activator
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
21)
pathways typically utilize
proteins that stimulate binding of RNA
polymerase to DNA.
A) Anabolic / repressor
B) Catabolic / repressor
C) Anabolic / activator
D) Catabolic / activator
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
22) In Bacteria, sensor kinases that respond to extracellular signals transfer this signal to the
cytoplasmic machinery by typically phosphorylating which residues?
A) Histidine
B) Serine
C) Threonine
D) Tyrosine
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.5
Learning Objective: 7.II
23) Quorum sensing is a regulatory system that requires a certain cell density to work effectively.
Each of the following activities utilizes quorum sensing EXCEPT
A) Staphylococcus aureus infection.
B) transition of Candida albicans from budding yeast to elongated filaments.
C) flagella synthesis in Proteus vulgaris.
D) light emission by Aliivibrio fischeri.
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.7
Learning Objective: 7.II
6
24) Chemotaxis in bacteria occurs through the use of
A) adaptation.
B) quorum sensing.
C) autoinduction.
D) a modified two-component system.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.6
Learning Objective: 7.II
25) Which statement is TRUE of two separate regulators controlling one individual operon?
A) The two regulators themselves must respond to different signals, which enables both to
control the operon differently.
B) One regulator will likely control the transcription of one section of the operon, whereas the
other regulator will control the other component.
C) One regulator will bind to the operator region whereas the other will bind to the promoter
region so they can co-occur and co-regulate the operon.
D) Two regulators trying to control the same operon will likely result in only one being
maintained after several generations.
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.6-7.8
Learning Objective: 7.II, 7.III
26) How would you design an sRNA to bind to a sequence?
A) Select six continuous nucleotides from the sequence
B) Take the complementary sequence of six continuous nucleotides
C) Select 200 continuous nucleotides from the sequence
D) Take the complementary sequence of 200 continuous nucleotides
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.12
Learning Objective: 7.IV
27) When the nontemplate strand of a gene is transcribed into RNA, what is likely to result?
A) A complementary sRNA will bind to it and form a functional ribozyme with secondary
structure.
B) It will complementarily bind to the gene sequence, form a hairpin loop, and transcriptionally
repress the gene.
C) The complementary mRNA transcribed from the template strand will bind to it and halt its
translation.
D) A global regulator will identify this as a stress, respond by inducing ribonuclease production,
and it will be degraded.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.12
Learning Objective: 7.IV
7
28) Based on our understanding of the early stages of life,
the earliest forms of metabolic regulation that evolved.
A) attenuation
B) feedback inhibition
C) riboswitches
D) transcription factors
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.13
Learning Objective: 7.IV
is/are thought to be one of
29) Attenuation is a type of regulation that can control
A) allosteric enzyme activity.
B) transcriptional activity exclusively.
C) translational activity exclusively.
D) both transcriptional and translational activity.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.14
Learning Objective: 7.IV
30) Which of the following is a characteristic of an isoenzyme?
A) More than one enzyme is regulated by the same mechanism.
B) The same reaction can be catalyzed by multiple enzyme variants.
C) Multiple binding sites on the same enzyme enable multiple regulation mechanisms.
D) More than one gene makes the same enzyme.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.15
Learning Objective: 7.V
31) Which regulatory mechanism does NOT depend on a conformational change in
protein/enzyme structure to change activity?
A) Attenuation
B) Catabolite repression
C) Feedback inhibition
D) Negative control
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.14
Learning Objective: 7.IV
8
32) An organism grown in nutrient rich broth to high turbidity always produces a blue pigment.
When a large inoculum is transferred to a nutrient rich agar plate, it also appears blue. A
researcher noticed that this never happens when very small colonies are grown on low nutrient
agar plates, however. What is the most plausible conclusion?
A) Large populations enabled the differentiation of a subpopulation of cells that created the blue
pigment.
B) Only high nutrient conditions provide enough energy for cells to produce this secondary
metabolite that appears blue.
C) Production of the blue pigment production is linked to quorum sensing.
D) The strong gradient from very high to low nutrient bioavailability induces production of the
blue metabolite.
Answer: C
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.7
Learning Objective: 7.II
33) A bacterium that either partially or fully catabolizes an acyl-homoserine lactone will likely
disrupt
A) attenuation.
B) chemotaxis.
C) endospore formation.
D) quorum sensing.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.7
Learning Objective: 7.II
34) Phosphorylation of
regulates which direction a flagellum rotates, thus controlling
whether an organism runs or tumbles.
A) CheAW
B) CheB
C) CheY
D) CheZ
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.6
Learning Objective: 7.II
35) Which organism would likely harbor the most two-component regulatory systems?
A) An archaeon living in an extreme environment
B) A bacterium occupying a heterogeneous niche with high nutrient mixing
C) An organism capable of quorum sensing
D) A parasitic bacterium living inside another organism
Answer: B
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.5
Learning Objective: 7.II
9
36) How is the activity of a riboswitch controlled?
A) By other riboswitches
B) Metabolite binding can change its structure.
C) Sigma factor binding alters its structure.
D) Small RNA complementary binding disrupts its function.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.13
Learning Objective: 7.IV
37) A mutation in the gene encoding the lactose repressor (LacI) that prevents lactose from
binding to the LacI protein would result in
A) constant expression of the lac operon in the absence of lactose.
B) constant repression of the lac operon in the absence of lactose.
C) constant expression of the lac operon in the presence of lactose.
D) constant repression of the lac operon in the presence of lactose.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.8
Learning Objective: 7.III
38) Why are two-component regulatory systems particularly useful for controlling gene
expression in response to environmental signals?
A) Two proteins controlling a gene means there are two chances to activate a gene.
B) Two proteins delay the response time so the cell can be sure the change is permanent.
C) One of the two proteins can be exposed to the external environment to receive a signal.
D) Phosphorylation is a permanent change so genes are always turned on after signal.
Answer: D
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.5
Learning Objective: 7.II
39) In order for the helix-turn-helix motif to bind to DNA, the
groove of the DNA.
A) homeotic switches
B) recognition helix
C) operator
D) zinc fingers
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
10
must fit into the major
40) Infection by the foodborne pathogen E coli O157:H7 involves all of the following host and
pathogen signaling molecules EXCEPT
A) AI-3.
B) MCP.
C) epinephrine.
D) norepinephrine.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.7, 7.10
Learning Objective: 7.II, 7.III
41) Global regulatory systems include all of the following EXCEPT
A) amino acid synthesis.
B) transformation.
C) heat shock response.
D) anaerobic respiration.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.8-7.11
Learning Objective: 7.III
42) When more than one operon is under the control of a single regulatory protein, the operons
are collectively called a(n)
A) regulon.
B) operator.
C) autoinduce.
D) riboswitch.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
43) Most riboswitches control
A) transcription.
B) translation.
C) ribosome synthesis.
D) tRNA synthesis.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.13
Learning Objective: 7.IV
11
44) PII proteins are a family of signal-transducing proteins that regulate _
nitrogen metabolism.
A) transcription factors
B) enzymes
C) membrane transport proteins
D) PII proteins regulate each of the above during nitrogen metabolism.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.16
Learning Objective: 7.V
during
45) All of the following are functions of heat shock proteins in bacteria EXCEPT
A) prevention of inappropriate protein subunit aggregation.
B) degradation of denatured proteins.
C) responding to exposure to high levels of ethanol.
D) stimulation of binary fission.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.11
Learning Objective: 7.III
7.2 True/False Questions
1) Proteins required at approximately the same level throughout a cell's growth cycle are often
not subject to regulatory mechanisms and are constitutively synthesized.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
2) Short regions at the beginning and end of gene sequences are not translated into proteins.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
3) Small molecules usually act directly (rather than indirectly) in regulating transcription.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
4) A common structure for proteins that bind DNA is helix-turn-helix.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
12
5) The residues in a DNA-binding protein that interact with DNA usually correspond to each
other according to the amino acids encoded by the DNA. For example, a DNA sequence
containing AGC-AGA-CAG which encodes for Ser-Arg-Gln would likely have a DNA-binding
protein with the sequence Ser-Arg-Gln.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.1
Learning Objective: 7.I
6) Some proteins that bind to DNA block transcription, whereas other proteins activate
transcription.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
7) Enzyme repression typically affects catabolic pathways.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.3
Learning Objective: 7.I
8) Depending on the type of regulatory mechanism, activators and repressors can bind to
operator regions which control transcription.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.2
Learning Objective: 7.I
9) A regulon is composed of at least two operons regulated by the same protein.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.3
Learning Objective: 7.I
10) The preferential use of glucose over other available carbon substrates for growth is
mechanistically explained by catabolite repression.
Answer: TRUE
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.8
Learning Objective: 7.III
13
11) Proteins and RNA molecules that are needed in the cell at about the same level under all
growth conditions, require constitutive expression.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1
Learning Objective: 7.I
12) A two-component regulatory system usually involves both the sensor and response proteins
being subject to phosphorylation.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.5
Learning Objective: 7.II
13) Cyclic AMP (cAMP) is involved in the global regulation of catabolic pathways in
Escherichia coli, including the lac operon. A high activity of the enzyme adenylate cyclase,
which makes cAMP, is suggestive of catabolite repression.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.8
Learning Objective: 7.III
14) Once cytoplasmic sensor proteins involved in chemotaxis regulation are phosphorylated, a
cascade of other phosphate-transferring mechanisms provides ATP to rotate flagella.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.6
Learning Objective: 7.II
15) In most cases, the first product of a particular biosynthetic pathway represses the enzymes of
the pathway.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.15
Learning Objective: 7.V
16) In catabolic repression, cells always use the least abundant carbon source first.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.8
Learning Objective: 7.III
14
17) The small size of prokaryotic cells limits their ability to respond to spatial gradients of a
chemical.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.6
Learning Objective: 7.II
18) Adaptation is based on the level of phosphorylation of MCPs.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.6
Learning Objective: 7.II
19) Quorum sensing relies upon a large cell population which then turns on transcription.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.7
Learning Objective: 7.II
20) During chemotaxis, attractants increase the rate of autophosphorylation, whereas repellants
decrease this rate.
Answer: FALSE
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.6
Learning Objective: 7.II
21) Heat shock proteins are produced in high number to minimize damaging effects during
high heat conditions, in addition to other stress signals unrelated to heat such as ultraviolet
radiation.Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.11
Learning Objective: 7.III
22) Regulation of transcription in Archaea is more similar to that which occurs in eukaryotes
than in bacteria.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.4
Learning Objective: 7.I
23) The stringent response is a mechanism used by bacteria that provides increased ability to
survive in environments lacking nutrients.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.9
Learning Objective: 7.III
15
24) When environmental levels of amino acids become limited, synthesis of mRNA, rRNA, and
tRNA increases immediately.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.9
Learning Objective: 7.III
25) In many environments, the limiting nutrient for bacterial growth is phosphorus.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.10
Learning Objective: 7.III
26) Multiple mechanisms for small RNA (sRNA)-mediated translational regulation exist, but all
are unified by inactivating protein synthesis of the target mRNA.
Answer: FALSE
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.12
Learning Objective: 7.IV
7.3 Essay Questions
1) Explain a common mechanism used by cells to ensure proper binding of DNA-binding
proteins to DNA.
Answer: DNA-binding proteins are proteins composed of DNA-binding domains and that have a
specific or general affinity for either single- or double-stranded DNA. One of the most common
domains is the helix-turn-helix structure, which consists of two segments of polypeptide chain
that have an α-helix secondary structure connected by a short sequence forming the "turn." The
first helix is the recognition helix, which interacts specifically with the DNA. The second helix is
the stabilizing helix, which stabilizes the first helix by interacting with it through hydrophobic
interactions. The turn linking the two helices consists of three amino acids with glycine typically
the first. Sequences are recognized by noncovalent interactions between the recognition helix of
the protein and specific chemical in the sequence of base pairs on the DNA.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.1, 7.2
Learning Objective: 7.I
16
2) Using the tryptophan operon as a model, describe the formation of a stem-loop structure and
its function.
Answer: A pause in mRNA transcription occurs when tryptophan is in short supply and
therefore requires the additional recruitment of a charged tryptophan tRNA for its synthesis. This
lag or pause time provides the already synthesized mRNA component to bind to a different part
of the transcript than would occur if there were no pause time. This different hairpin loop formed
does not interact with the DNA sequence and therefore permits RNA polymerase to continue
transcribing the entire mRNA, unlike what would occur if a lag time were absent.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.14
Learning Objective: 7.IV
3) Explain the phenomenon known as diauxic growth. Hypothesize why this type of regulation
might be important for the survival of a microbe in a mixed population.
Answer: Consider Escherichia coli as an example: when Escherichia coli is exposed
simultaneously to both glucose and lactose, it will preferentially use glucose before lactose.
Diauxic growth therefore explains how cells control gene expression, often as operons and
regulons, to achieve the fastest growth rate. If a cell were to not have this mechanism, it might be
outcompeted in the environment by other faster growing and replicating cells. Lacking a global
catabolite regulation system might be advantageous for cells occurring in a mixed population
where competition for a single substrate could provide poor growth yields.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.8
Learning Objective: 7.III
4) Describe the basic two-component regulatory system, and explain the function of each
component.
Answer: The first component of the system involves a specific sensor kinase protein located in
the cytoplasmic membrane which receives an external environmental signal. The kinase
autophosphorylates itself once signaled and creates a phosphate ion for the second component. A
response regulator protein within the cell's cytoplasm then binds the phosphate ion and
ultimately binds DNA. The regulation in response to this DNA binding can either be positive or
negative, depending on the system.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.5
Learning Objective: 7.II
5) Explain why is it not surprising that two-component regulatory systems are all but absent in
bacteria that live at the expense of a host.
Answer: Answers will vary, but a possible explanation is that an organism that has adapted to
living inside of a host has such a narrow metabolic capacity that responses to nutrient limitation
are less necessary than a bacterium growing in a dynamic community.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.5
Learning Objective: 7.II
17
6) Explain why one cell of a pathogenic bacterium by itself typically does not secrete a toxin,
despite the species as a whole being characterized as toxin producing. To help in your
explanation, predict what would happen to an individual pathogen that secreted a toxin inside a
human.
Answer: One pathogenic bacterium is unlikely to be able to produce a sufficient number of toxin
molecules to cause a disease. Once the bacterium grows to a sufficient quantity that it can cause
disease through the production of toxins, coordination of toxin production by the population is
performed by quorum sensing. The production of a toxin by a single cell would likely alert the
immune system a foreign bacterium is present and would be killed by a healthy immune system.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.7
Learning Objective: 7.II
7) How is transcription in Archaea controlled?
Answer: Archaea have mechanisms to control transcription, which are most similar to those
found in Bacteria rather than other mechanisms such as those in Eukarya. They contain both
activators and repressors, which can regulate RNA polymerase activity in either a positive or
negative way.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.4
Learning Objective: 7.I
8) Contrast prokaryotic and eukaryotic regulation of gene expression.
Answer: In Bacteria and Archaea, a common mechanism for regulation of RNA polymerase
activity is to use DNA-binding proteins that either block RNA polymerase activity (repressor
proteins) or stimulate RNA polymerase (activator proteins). An alternative mechanism found
commonly in eukaryotes is to coordinate numerous DNA-binding proteins known as
transcription factors to interact with RNA polymerase.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.1, 7.2, 7.4
Learning Objective: 7.I
9) Explain the function of cAMP in catabolite repression.
Answer: Adenylate cyclase synthesizes the regulatory nucleotide cAMP, and when the substrate
glucose is present this process is inhibited (or repressed). This means glucose is a preferred
substrate for catabolism in cells that contain this mechanism, such as E. coli. Once glucose has
been used up, cAMP is then produced, which forms a cAMP-CAP-DNA complex, resulting in
transcription of the genes that the CAP corresponds to, and catabolism of an additional substrate
can be performed.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.8
Learning Objective: 7.III
18
10) A cocktail of 30 compounds was identified to harbor a corepressor, and subsequent
separation and purification was performed to test individual compounds. Describe an experiment
that would enable you to identify the specific compound that acts as a corepressor for a catabolic
pathway. Be certain to explain what will be measured and how you could conclude which
compound is a corepressor.
Answer: Experimental designs will vary, depending on whether transcripts, proteins, or enzyme
function is quantified. Measurement of each would enable measuring activity of the repressor. In
each case, a compound added to the system which shows significantly lower (basal) activity
would indicate it is a corepressor. Compounds that do not act as a corepressor would result in no
change in activity, meaning transcripts, proteins, and enzyme function would still be observed.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.2
Learning Objective: 7.II
11) In considering the function of heat shock proteins, why is it not surprising that these proteins
are both highly conserved and very ancient? Provide your reasoning.
Answer: Answers will vary, but one idea is for an organism to survive in the environment, it
must be able to survive unfavorable conditions. Recognizing that heat shock proteins generally
facilitate the refolding or removal of misfolded proteins, whether it be from heat or other
conditions, it makes sense these are so critical for a cell to survive that they would have needed
to be present even in ancient organisms. Additionally, whether a protein is misfolded in a
eukaryote or a prokaryote, it seems likely that a heat shock protein would be needed to refold it.
These proteins may be similar, which explain the high conservation throughout all life forms.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.11
Learning Objective: 7.III
12) Provide evidence that supports the hypothesis that riboswitches are remnants of the RNA
world when catalytic RNAs were the only self-replicating life forms.
Answer: Answers will vary, but one focus could be on their presence in bacteria that are
considered to have evolved well before Eukarya, yet riboswitches are generally lacking in
eukaryotes. If no other life forms were around and RNA was the only replicating form, the
function of riboswitches could explain a (primitive) mechanism to control its own synthesis.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.13
Learning Objective: 7.III
19
13) Compare and contrast chemical, spatial, and temporal gradients as found in bacterial
regulatory systems.
Answer: Bacteria cannot sense spatial gradients of chemicals due to their small size, so they are
capable only of determining a chemical gradient over time. That is, they can sense the change in
concentration of a chemical over time rather than the absolute concentration of the chemical
stimulus. These temporal changes of a chemical are sensed with a two-component system. In the
example of chemotaxis, an attractant or repellant's presence results in a change in activity of preexisting flagella.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 7.6
Learning Objective: 7.II
14) Two common levels of regulation of protein activity are transcriptional control and
posttranslational control. Discuss the differences between the two in terms of speed of response
and energy efficiency.
Answer: Transcriptional control will be the slowest (the gene needs to be transcribed, the
mRNA translated, and the protein correctly folded before protein activity) but is the most energy
efficient because proteins are only made when they are needed. Posttranslational control is the
fastest (the protein is already synthesized; it just needs a modification) but is less energy efficient
because a protein might be made and degraded before it ever gets activated.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.2, 7.3, 7.16
Learning Objective: 7.I, 7.V
15) Many of the virulence factors produced by the opportunistic pathogen Pseudomonas
aeruginosa are the result of quorum sensing. What role do autoinducers play in this mechanism
of bacterial pathogenicity?
Answer: Through the use of autoinducers, bacteria can regulate their behavior according to
population density. The phenomenon of quorum sensing relies on the principle that when a
single bacterium releases autoinducers (AIs) into the environment, their concentration is too low
to be detected. However, when sufficient bacteria are present, autoinducer concentrations reach a
threshold level that allows the bacteria to sense a critical cell mass and, in response, to activate or
repress target genes including those of various virulence factors.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.7
Learning Objective: 7.II
20
16) Describe the difference between constitutive and inducible genes. Based on your knowledge
of bacterial cells, give an example of each.
Answer: Constitutive genes are those which are transcribed at a relatively constant level
regardless of the cell's environmental conditions. These genes are sometimes referred to as
"housekeeping genes" and include genes for heat shock proteins such as DnaK in Escherichia
coli. The expression of inducible genes is highly regulated and these genes must be able to be
rapidly and specifically activated in response to environmental stimuli. Examples of inducible
genes would include those coding for activator and repressor proteins.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.1
Learning Objective: 7.I
17) What are sigma factors? Explain the roles of the two different sigma factors known as RpoH
and RpoS.
Answer: A sigma factor (σ factor) is a protein needed only for initiation of RNA synthesis. The
specific sigma factor used to initiate transcription of a given gene will vary, depending on the
gene and on the environmental signals needed to initiate transcription of that gene. RpoH is the
heat shock sigma factor and is turned on when bacteria are exposed to heat. RpoS is highly
expressed during the transition from the exponential to stationary phase of the bacterial growth
curve.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 7.11
Learning Objective: 7.III
18) What would be the result of a mutation that results in the inactivation of the Tar MCP in
Escherichia coli?
Answer: The mechanism of chemotaxis depends upon a signal cascade of multiple proteins.
These sensory proteins allow the cell to monitor the concentration of various substances over
time and are called methyl-accepting chemotaxis proteins (MCPs). The Tar MCP produced by
Escherichia coli senses aspartate and maltose and the repellants cobalt and nickel. Binding of an
attractant or repellant triggers interactions with the cytoplasmic proteins that affect flagellar
rotation. A mutation in the gene for Tar MCP would result in inability to move toward aspartate
and maltose or away from cobalt and nickel.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.6
Learning Objective: 7.II
19) Explain how adaptation of the chemotaxis system is achieved once an organism has
responded to a stimulus.
Answer: Once an organism has successfully responded to a stimulus, it must stop responding
and reset the sensory system until a further signal is received. During adaptation of the
chemotaxis system, a feedback loop that relies on the response regulator CheB resets the system.
This is accomplished by methylation and demethylation of the MCPs by CheR and
phosphorylated CheB respectively.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 7.6
Learning Objective: 7.II
21
Brock Biology of Microorganisms, 16e (Madigan et al.)
Chapter 9 Genetics of Bacteria and Archaea
9.1 Multiple Choice Questions
1) A mutant that has a nutritional requirement for growth is an example of a(n)
A) autotroph.
B) auxotroph.
C) heterotroph.
D) organotroph.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.1
Learning Objective: 9.I
2) Consider a mutation in which the change is from UAC to UAU. Both codons specify the
amino acid tyrosine. Which type of point mutation is this?
A) Silent mutation
B) Nonsense mutation
C) Missense mutation
D) Frameshift mutation
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.2
Learning Objective: 9.I
3) A mutation that readily reverses to restore the original parental type would most likely be due
to a(n)
A) deletion.
B) insertion.
C) point mutation.
D) frameshift mutation.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.2
Learning Objective: 9.I
4) Which process listed below allows genetic material to be transferred from a virus-like particle
that lacks genes for its own replication?
A) Conjugation of an F+ plasmid
B) Gene transfer through a gene transfer agent
C) Transduction by a dsDNA phage Mu
D) Transformation of a linear piece of DNA
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
1
5) The mutagens 2-aminopurine and 5-bromouracil are examples of
A) alkylating agents.
B) nucleotide base analogs.
C) chemicals reacting with DNA.
D) None of the answers are correct.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
6) The killing of cells by UV irradiation involves
A) absorption at 260 nm by proteins only.
B) absorption at 260 nm by RNA only.
C) formation of pyrimidine dimers.
D) formation of purine dimers.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
7) Ionizing radiation does NOT include
A) gamma rays.
B) UV rays.
C) X-rays.
D) cosmic rays.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
8) Which of the following methods may introduce foreign DNA into a recipient?
A) Transformation
B) Transduction
C) Conjugation
D) Transformation, transduction, and conjugation
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6, 9.7, 9.8
Learning Objective: 9.II
2
9) The uptake of free DNA from the environment is referred to as
of DNA with cell-to-cell contact is known as
.
A) transformation / conjugation
B) transduction / conjugation
C) conjugation / transformation
D) transformation / transduction
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6, 9.8
Learning Objective: 9.II
, while the transfer
10) Which of the following is NOT required for homologous recombination?
A) An Hfr chromosome
B) RecA
C) Proteins having helicase activity
D) Endonuclease
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.5
Learning Objective: 9.II
11) Consider the following experiment. First, large populations of two mutant strains of
Escherichia coli are mixed, each requiring a different, single amino acid. After plating them onto
a minimal medium, 45 colonies grew. Which of the following may explain this result?
A) The colonies may be due to back mutation (reversion).
B) The colonies may be due to recombination.
C) Either A or B is possible.
D) Neither A nor B is possible.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.3-9.5
Learning Objective: 9.I, 9.II
12) You have performed the following mating experiment using Hfr and F-strains of Escherichia
coli: Hfr (thr + leu+ gal+ strs) × F- (thr- leu- gal- strr). Which of the following selective media
would you use to score recombinant colonies?
A) Minimal medium
B) Minimal medium + streptomycin
C) Minimal medium + threonine
D) Minimal medium + streptomycin + threonine
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.5, 9.9
Learning Objective: 9.II
3
13) Horizontal gene transfer in Archaea
A) is infrequent in nature and therefore difficult to use for genetic studies in the laboratory.
B) has not been documented, thus all genetic studies of archaea are done via genomic
sequencing.
C) frequently occurs in nature and has been used to perform genetic studies in the laboratory as
well.
D) frequently occurs in nature, but there are very few laboratory studies because archaea do not
cause human disease.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.10
Learning Objective: 9.III
14) The minimal amount of genetic information required for specialized transduction would
include
A) the att region.
B) the cos site.
C) a helper phage.
D) the att region, cos site, and a helper phage.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
15) Lysogeny probably carries a strong selective advantage for the host cell because it
A) prevents cell lysis.
B) confers resistance to infection by viruses of the same type.
C) confers resistance to infection by viruses of a different type (or strain).
D) confers resistance to infection by many virus types and prevent cell lysis.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
16) A plasmid may
A) replicate independently of the chromosome.
B) be transferred cell-to-cell during conjugation.
C) be integrated into the chromosome.
D) replicate independently of the chromosome, integrate into the chromosome, or be transferred
cell-to-cell during conjugation.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
4
17) Plasmids that govern their own transfer are known as
A) transformable.
B) transmutable.
C) conjugative.
D) transfective.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8
Learning Objective: 9.II
18) Homologous recombination has been observed in
A) Archaea.
B) Bacteria.
C) Eukarya.
D) All three domains (Archaea, Bacteria, and Eukarya).
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.5
Learning Objective: 9.II
19) Hfr strains of Escherichia coli
A) do not possess an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the complete F factor to recipient cells at a high frequency.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
20) F+ strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to recipient cells at a high frequency.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8
Learning Objective: 9.II
5
21) F- strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to other strains at a high frequency.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8
Learning Objective: 9.II
22) All Hfr strains integrate into the chromosome at
A) the same locus.
B) several specific sites.
C) the same locus most of the time, although there may be some variation.
D) loci that cannot be accurately determined.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
23) Transposition is a(n)
A) homologous recombination event.
B) analogous recombination event.
C) site-specific recombination event.
D) general recombination event.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
24) The enzyme transposase may be coded for by insertion sequences on a
A) chromosome.
B) phage.
C) plasmid.
D) chromosome, phage, or plasmid.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
6
25) A ʺpoint mutationʺ refers to mutations involving
A) a base-pair substitution.
B) the gain of a base pair (microinsertion).
C) the deletion of a base pair (microdeletion).
D) a substitution, deletion, or addition of one base-pair.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.2
Learning Objective: 9.I
26) A deleterious mutation in recA results in
A) a decrease in specific recombination.
B) a decrease in homologous recombination.
C) an increase in homologous recombination.
D) no change in either general or specific recombination.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.4
Learning Objective: 9.I
27) The production of a functional gene product by transforming bacteria that lack a lacZ gene
with a plasmid containing a lacZ gene is known as
A) complementation.
B) mitosis.
C) transfection.
D) reversion.
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.5
Learning Objective: 9.II
28) Consider conjugation in Escherichia coli. In which of the following matings would
chromosomal genes be transferred most frequently?
A) F+ × FB) F- × FC) Hfr × FD) F+ × F+
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.9
Learning Objective: 9.II
7
29) Which of the following features are common to transformation, transduction, and
conjugation?
(1) Unidirectional transfer of genes
(2) Incomplete gene transfer
(3) Homologous recombination
(4) Meiosis occurring in the recipient
A) 1, 2, 3
B) 1, 2
C) 3, 4
D) 1, 2, 4
Answer: A
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.6-9.8
Learning Objective: 9.II
30) Which of the following is most similar to lysogeny?
A) Hfr state
B) F+ state
C) F- state
D) F' state
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.9
Learning Objective: 9.II
31) In the bacterial world, a gene located on which of the following would be the LEAST likely
to be transferred?
A) A resistance plasmid
B) An F plasmid
C) The phage Mu
D) The chromosome
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.5-9.9
Learning Objective: 9.II
32) Genetic recombination involving insertion sequences typically results in what type of
mutation?
A) Base-pair substitution mutation
B) Silent mutation
C) Frameshift mutation
D) Base-pair deletion mutation
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.2
Learning Objective: 9.I
8
33) The SOS regulatory system is activated by
A) the activity of DNA polymerase IV.
B) DNA damage.
C) transcription of LexA.
D) repression of RecA.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
34) Which of the following factors has delayed the development of laboratory-based genetic
systems in Archaea?
A) There are no documented systems of conjugation in Archaea.
B) Homologous recombination does NOT occur in Archaea.
C) Archaea do NOT host viruses or plasmids.
D) Many Archaea grow in extreme or unusual conditions that make the use of agar and
traditional mutant screening techniques problematic.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.10
Learning Objective: 9.III
35) Transformation and homologous recombination allow for the formation of heteroduplex
DNA. Which of the following would occur during DNA replication of this molecule?
A) One daughter strand is complementary to the recombinant DNA molecule, while the other
daughter strand is complementary to the parent DNA molecule.
B) Both daughter strands are complementary to the recombinant DNA molecule.
C) Both daughter strands are complementary to the parent DNA molecule.
D) None of the answers are correct.
Answer: A
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.6
Learning Objective: 9.II
9
36) You work for a biotechnology company that uses Streptomyces strains to produce
pharmaceutical products. A phage has infected and killed some of your Streptomyces strains
during production, resulting in dramatically decreased yields. To protect the strains from
infection you propose to
A) introduce gene transfer agents into the Streptomyces cultures to transfer antibiotic resistance
genes into your Streptomyces strains.
B) design and insert CRISPR spacer sequences into the genomes of your strains that are
complementary to the genomes of the phages that are infecting the cultures.
C) infect the Streptomyces strains with a helper phage that will help the strains resist infection.
D) transform the Streptomyces strains with plasmids encoding antibody proteins that will protect
them from phage infection.
Answer: B
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.12
Learning Objective: 9.III
37) Hfr means high frequency of
, and these cells are capable of transferring genes
from their
to other cells.
A) transformation / chromosome
B) recombination / plasmids
C) recombination / chromosome
D) transduction / chromosome
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
38) Mutation rates are similar in Bacteria and Archaea, yet under certain stressful conditions
mutation rates increase. Why is the mutation rate not constant and close to zero all of the time?
A) Increased mutation rates can be advantageous in rapidly changing environments because
some random mutations may be useful for survival.
B) Microorganisms carefully control the mutation rate of their DNA to match the environmental
conditions and maximize evolution.
C) The increased mutation rate under stressful conditions is an indication that the
microorganisms can no longer replicate their DNA properly and are about to die.
D) Constant mutation rates would halt evolution completely.
Answer: A
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.3
Learning Objective: 9.I
10
39) Chemical mutagens, UV radiation, and ionizing radiation all increase mutation rates, but they
have different mechanisms. Which type of mutagen would be best suited for creating large
deletions and rearrangements within a genome?
A) Chemical mutagens
B) UV radiation
C) Ionizing radiation
D) Chemical, UV, and ionizing radiation would create large deletions and rearrangements if used
in a very high dose.
Answer: C
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.4
Learning Objective: 9.I
40) The SOS system repairs DNA that has gaps, breaks, and other lesions by
A) cutting DNA from other parts of the genome and pasting it into the gaps or damaged areas.
B) stabilizing single-stranded DNA until the next round of normal replication.
C) using specialized DNA polymerases that will synthesize a new DNA strand even if there
is not a normal complementary DNA strand to act as a template.
D) using available mRNA and a special RNA-dependent DNA polymerase to fill in the gaps and
replace damaged DNA.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
41) Microinsertions and microdeletions often result in
A) auxotrophic
B) advantageous
C) silent
D) frameshift
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.2
Learning Objective: 9.I
mutations.
42) When damaged or single-stranded DNA activates the RecA protein, the RecA protein
stimulates the cleavage of LexA. This results in
A) repression of polymerase V and activation of endonuclease.
B) activation of the Hfr system.
C) derepression of the SOS system.
D) increased transduction and recombination.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
11
43) The F (fertility) plasmid contains a set of genes that encode for the
are essential in conjugative transfer of DNA.
A) pili
B) SOS repair
C) transduction
D) transformation
Answer: A
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8
Learning Objective: 9.II
proteins that
44) The designations Phe-, Leu-, and Ser+ refer to an organism's
A) plasmid type.
B) genotype.
C) phenotype.
D) mutation type.
Answer: C
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.1
Learning Objective: 9.I
45) If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium
without ampicillin, it may
A) gain resistance to other antibiotics.
B) transfer resistance to other cultures in the laboratory.
C) undergo a reversion mutation.
D) lose the plasmid because there is no selection for ampicillin resistance.
Answer: D
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.3
Learning Objective: 9.I
46) When DNA is transferred into a prokaryotic cell, it may
A) be degraded by enzymes.
B) replicate independent of the host chromosome.
C) recombine with the host chromosome.
D) be degraded by enzymes, replicate independent of the host chromosome, or recombine with
the host chromosome.
Answer: D
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.12
Learning Objective: 9.III
12
47) The process in which related DNA sequences from two different sources are exchanged is
called
A) transduction.
B) phage conversion.
C) reversion.
D) homologous recombination.
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.5
Learning Objective: 9.II
48) Integration of linear transforming DNA into the chromosome
A) is not required for the expression for the transformed genes.
B) is catalyzed by the RecA gene.
C) almost never occurs because restriction endonuclease will degrade the DNA before it is
integrated.
D) only occurs in laboratory-based systems in artificial competent cells.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6
Learning Objective: 9.II
49) High-efficiency, natural transformation
A) is common in Bacteria and Archaea.
B) requires specialized DNA uptake, DNA binding, and integration proteins.
C) is only common in Archaea.
D) usually involves plasmids.
Answer: B
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.6
Learning Objective: 9.II
50) The CRISPR system
A) facilitates homologous recombination through a complex system of proteins and clustered
repeats.
B) recognizes foreign DNA sequences that have previously entered the cell and directs the Cas
proteins to destroy them.
C) repairs DNA and increases DNA damage tolerance during times of stress.
D) synthesizes gene transfer agents during stationary phase.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.12
Learning Objective: 9.III
13
51) Which of the following is the correct abbreviation for a mutation in a gene that synthesizes
one of the enzymes involved in tryptophan production?
A) TrpC
B) trp
C) TrpD) trpC1
Answer: D
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.1
Learning Objective: 9.I
52) Which of the following is FALSE of competence?
A) It is required for transformation.
B) It commonly occurs with high efficiency in nature.
C) It cannot occur naturally in bacteria.
D) It requires special proteins such as a cell wall autolysin.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6
Learning Objective: 9.II
53) What is one of the changes that occurs when a cell contains an F plasmid that is NOT
integrated into the chromosome?
A) It is no longer able to produce a pilus.
B) Cell surface receptors change, preventing the uptake of more plasmids through conjugation.
C) Mutation rates are decreased.
D) The cell is considered an Hfr cell.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
54) Horizontal gene transfer
A) is rare and only occurs between closely related strains.
B) is common and may sometime occur between unrelated organisms.
C) does not provide an advantage to organisms.
D) only occurs in prokaryotes.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
14
55) Horizontal gene transfer has been thoroughly documented for genes involved in
A) DNA replication and repair.
B) virulence and metabolic functions.
C) only very few processes.
D) translation.
Answer: B
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4, 9.7
Learning Objective: 9.I, 9.II
9.2 True/False Questions
1) UV radiation is a useful tool in producing mutants of microbial cultures.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
2) When UV radiation damage occurs, DNA repair occurs only in the absence of template
instruction.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
3) Following uptake, transforming DNA becomes attached to a competence-specific protein that
prevents it from nuclease attack until it reaches the chromosome.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6
Learning Objective: 9.II
4) The evolutionary significance of phage conversion likely stems from an effective alteration of
host cells.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
5) Bacterial mating (or conjugation) is a bidirectional process where nucleic acids (DNA or
RNA) are transferred between two cells.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8
Learning Objective: 9.II
15
6) Laboratory-based genetic systems have been difficult to develop for Archaea, because they do
NOT naturally undergo conjugation or transduction.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.10
Learning Objective: 9.III
7) Selective pressure must be maintained on a cell for that cell to retain its plasmid.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.1, 9.5
Learning Objective: 9.I, 9.II
8) Most plasmids are circular rather than linear.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.8, 9.9
Learning Objective: 9.II
9) When the F factor is integrated, all Hfr strains have the origin of replication functioning in the
same direction.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
10) In a prokaryotic genome, either insertion elements OR transposons are present, but both are
never present at the same time.
Answer: FALSE
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.11
Learning Objective: 9.III
11) The use of transposons to generate mutations is a convenient way to create bacterial
mutations in the laboratory.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
12) Transposons can be found on many genetic elements, including plasmids, chromosomes, and
viral genomes.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
16
13) In transformation experiments using a variety of Bacteria, it has been noted that essentially
all of the cells in a population can become competent.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6
Learning Objective: 9.II
14) In specialized transduction, virtually any genetic marker can be transferred from donor to
recipient.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
15) In specialized transduction, as exemplified by lambda phage in E. coli, transduction occurs at
high efficiency for only a restricted group of genes near the insertion site of lambda.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
16) Many Bacteria isolated from nature are natural lysogens.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
17) Lysogeny is essential for the virulence of many pathogenic bacterial strains.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
18) Proteins and nucleic acids absorb light maximally at 260 nm; hence, proteins protect cells
from UV effects.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
19) Insertion sequences are found on both ends of transposons and encode for transposase.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
17
20) Toxigenicity in Corynebacterium diphtheriae is due to phage conversion.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
21) All Hfr strains possess an F factor integrated into the host chromosome.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.9
Learning Objective: 9.II
22) Intercalating agents, like acridine orange and ethidium bromide, lead to mutagenesis by
pushing DNA base pairs apart, which can lead to insertions or deletions.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.4
Learning Objective: 9.I
23) A typical mutation rate for a bacterium is in the range of 10-6 to 10-7 per kbp.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.3
Learning Objective: 9.I
24) Archaea have a unique form of conjugation involving cytoplasmic bridges for bidirectional
transfer of DNA.
Answer: TRUE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.11
Learning Objective: 9.III
25) A phage can be infectious even if all of its DNA has been replaced by bacterial DNA.
Answer: FALSE
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.7
Learning Objective: 9.II
18
9.3 Essay Questions
1) Design an experiment (including controls) to determine if a new kitchen chemical cleaner is
mutagenic. Include in your answer how you would interpret the results.
Answer: The Ames test could be used to determine if the cleaner solution causes mutations in
bacteria. An auxotrophic mutant strain (e.g., Salmonella enterica His-) containing a point
mutation is most helpful for this test, so it can measurably revert in small populations of cells. A
His- cell population exposed to various concentrations of the cleaner solution would then be put
into agar plates lacking histidine, and the number of colonies that grew would represent cells that
mutated back to wildtype (His+). An important control for the test is to plate an equal number of
cells not exposed to the cleaner solution on to the same medium to calculate a baseline mutation
rate of the cells when not exposed to the chemical cleaner. If there are significantly more His+
revertants that grew after exposure to the cleaner solution, then the chemical is mutagenic.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.2
Learning Objective: 9.I
2) Explain how electroporation works and the significance of the procedure for genetic
experiments.
Answer: Electroporation involves pulsing cells with a high voltage. The brief electrical charge
makes cells temporarily permeable such that foreign DNA (e.g., plasmids) can be taken up.
Electroporation can be used to introduce circular pieces of dsDNA into cells that are not
naturally competent, such as gram-negative bacteria and some species of Archaea. This process
yields artificially constructed transformants and is a key step in genetic manipulation.
Bloom's Taxonomy: 1-2: Remembering/Understanding
Chapter Section: 9.6
Learning Objective: 9.II
3) Compare and contrast generalized transduction with specialized transduction.
Answer: Transduction as a whole is the transfer of genetic information from one cell to another
mediated by a virus. Generalized transduction allows for any portion of a cell's genome to be
transferred, but this process occurs at a very low frequency (roughly 10-6 to 10-8). Specialized
transduction transfers only genetic material adjacent to the integrated phage (prophage),
however, its transfer efficiency is much higher than in generalized transduction.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.7
Learning Objective: 9.II
19
4) Consider the map shown below of a portion of a prokaryotic genome. How might the elements
indicated affect the stability and structure of the genome? Assume that IS2 encodes for a
transposase that catalyzes conservative transposition. Re-draw the genome map to illustrate your
prediction if necessary.
| IS2 | gene1 gene2 gene3 | IS2 | geneA geneB geneC | IS2 | geneD | IS2 | geneX
Answer: Answers should indicate that having multiple IS2 elements in the genome could result
in the deletion and/or rearrangement of gene order by transposition events. Composite
transposons can form if the genes between to insertion sequences move, or transpose, with the
insertion sequences. For instance, geneD could be removed from this part of the genome and
inserted elsewhere. OR geneABCD could all move together to another part of the genome
through transposition. Similarly, gene123 could move together, or even gene123 and geneABCD
(but not geneX). If conservative transposition is the only possibility, then the genes will move
from one spot to another in the genome, but if replicative transposition occurred the genes could
be copied to another part of the genome.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.11
Learning Objective: 9.III
5) Discuss the importance of homologous recombination and transposition in natural horizontal
gene transfer and evolution. Be sure to define all of the terms you use and connect them together
logically in your answer.
Answer: Natural horizontal gene transfer is the movement of genes between cells that are not
direct descendants of each other. Three mechanisms (transduction, transformation, and
conjugation) can transfer genetic material between cells. Once the genetic material is in a cell, it
is not necessarily passed down to daughter cells unless it can replicate on its own or is integrated
into the genome. Homologous recombination combines similar DNA molecules from two
different sources, thus homologous recombination aids in the integration of transferred genetic
material into the recipient cell. Transformation also can move segments of DNA between two
genetic elements, thus transformation also aids in the movement of genes from temporary or
separate genetic elements into the genome of a recipient. Without homologous recombination
and transposition, horizontal gene transfer would result in fewer permanent or heritable genetic
changes. Thus without homologous recombination and transposition, horizontal gene transfer
would have a lesser effect on evolution.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.5, 9.11
Learning Objective: 9.II, 9.III
20
6) Why is the outcome of a base-pair substitution mutation variable? List and describe the
possible outcomes of a base-pair substitution mutation in your answer.
Answer: The outcome of a base-pair substitution mutation is variable because multiple codons
can code for the same amino acid. For example, ACC, ACG, and ACU all encode for alanine
(codon examples do not necessarily have to be correct, but should convey the concept). Often the
third position of the codon can change without changing the amino acid. In addition, some amino
acids have similar properties (e.g., leucine and isoleucine), thus changing particular amino acids
may not have much of a phenotypic affect. There are three possible outcomes of a point
mutation. Silent mutations can have slightly modified protein structures or unmodified ones, as
long as the nucleotide change does not result in any change of the phenotype. Missense
mutations are more restricted in that a nucleotide change results in a particular amino acid
(codon) change. Although a missense mutation will change the amino acid sequence, this again
may or may not change the structure of the protein and the phenotype. A nonsense mutation is
the most specific of all where the nucleotide sequence now contains an inserted nonnative stop
site. The premature halt of protein synthesis will result in a shortened protein structure and will
likely change the phenotype of the organism.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.2
Learning Objective: 9.I
7) How does the SOS system simultaneously fix damage DNA and increase the mutation rate?
How does the SOS system increase the survival of microorganisms?
Answer: The SOS system causes the expression of a number of proteins, and specifically DNA
polymerases, that fix lesions in DNA molecules but are prone to errors or do not use templates at
all to synthesize new DNA. This allows the organism to survive DNA damage by fixing large
lesions or breaks in the DNA but also results in mutations. Even under some conditions that do
not result in a lot of DNA damage, the SOS system proteins can increase mutation rate. A slight
increase in mutation rate may increase the probability of an advantageous mutation in one cell
(even if many other cells are disadvantaged or killed by mutations). The cell with the
advantageous mutation would be better able to survive the stress and could go on to replicate and
take over the population, thus increasing the survival of the microorganism.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.4
Learning Objective: 9.I
21
8) A mutant you made in the laboratory with 5-bromouracil suddenly regains the wild-type
phenotype. You discuss this phenomenon with your advisor and colleagues, and they suggest
you try transposon mutagenesis to avoid this problem and create stable mutants. Why would
mutants created with 5-bromouracil be more likely to regain the wild-type phenotype than
mutants created via transposon mutagenesis?
Answer: Because a point mutation involves only a single base-pair change, reversion is quite
common relative to fixing an insertion of several nucleotides. Also common in Bacteria are
suppressor mutations, which suppress the initial mutation and restore the wild-type phenotype
(but not genotype) of a point mutation. However, no analogous mechanism works to fix largescale insertions or deletions
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.11
Learning Objective: 9.III
9) The CRISPR system is said to protect or preserve genome integrity in prokaryotic cells by
acting as a type of ʺimmune system.ʺ Explain how the CRISPR system works and its limitations.
Answer: The CRISPR (clustered regularly interspaced short palindromic repeats) system is
based on a region of the genome that contains DNA sequences from previously encountered
foreign DNA separated by short palindromic repeats. The CRISPR region is translated into a
long RNA molecule and then cleaved at each palindromic repeat to create short RNA molecules
(crRNAs) that are complementary to foreign nucleic acids. If the crRNA binds to a piece of
nucleic acid, associated proteins called Cas proteins will destroy the foreign nucleic acid and
prevent it from recombining with the genome or replicating. The CRISPR system only works if
the foreign DNA has homology with the DNA sequences in the CRISPR region of the genome.
This means that novel phages or other DNA sequences would not be recognized or destroyed.
Another limitation is that the CRISPR system might destroy DNA that contains useful genes or
sequences if it were allowed to recombine with the genome. This could slow down evolution and
adaptation.
Bloom's Taxonomy: 3-4: Applying/Analyzing
Chapter Section: 9.12
Learning Objective: 9.III
10) How might mutations in the dnaQ sequence, whose enzyme is involved in DNA
proofreading, be beneficial for a microbe in a highly competitive and dynamic community?
Answer: Mutations in dnaQ would result in an increase in mutation rate; however, unrepaired
mutations are not always lethal. In this situation, mutagenesis might be thought of as creating
diversity of a microbe's genome. Genetic diversity might create a genotype different enough that
a new phenotype arises. If, for example, the new phenotype is an ability to catabolize a particular
compound, this could provide the cell with the ability to survive using a different substrate for
energy when others are limited. Also, if a certain cell surface component is the target for phage
infection and lysis, a different gene sequence could modify the surface component to perhaps
enhance survivability in the environment.
Bloom's Taxonomy: 5-6: Evaluating/Creating
Chapter Section: 9.4
Learning Objective: 9.I
22