Midterm exam #1 of BIO3124 : General Microbiology
Name :
Student number :
This exam has two parts. The first part, which is worth 25 points, consists of 25 multiple choice
questions.
The second part, worth 15 points, includes 4 short answer questions. ONLY answer 3 of the 4
questions, or else only the first three will be corrected.
Part 1. Multiple choice questions
1. Which of the following conclusions would be false according to the observations made by
Jan Baptista Van Helmont concerning sponateous generation?
a.
b.
c.
d.
The spontaneous generation of life is specific to the ingredients used.
Life can only be created from inert materials.
Life is generated by the transformation of primary ingredients.
The spontaeous generation of life gives rise to organisms of both sexes.
2. To which domain does a cell with the following characteristics belong too? Has a nucleus, is
puprple by Gram staining, and is not part of a multicellular organism.
a.
b.
c.
d.
Eucarya.
Fungi.
Animalia.
Plantae.
3. The bacteria in this image belong to which genus and should be
what color following a typical Gram stain?
a.
b.
c.
d.
Micrococcus – Purple.
Streptococcus – Purple.
Escherichia – Red.
Bacillus – Colorless.
4. The cells in the above image would be what color if the safranin
was omitted from the Gram staining?
a.
b.
c.
d.
Puprple.
Red.
Colorless.
Blue.
5. Which of the following characteristics is not typical of the bacteria in the above image?
a.
b.
c.
d.
Techoic acid.
Peptidoglycan units conatining diaminopimelic acid (DAP).
A low level of proteins in their cell wall.
A glycine bridge linking the peptidoglycan polymers.
6. The above bacteria divide themselves along how many axes?
a.
b.
c.
d.
Four.
One.
Three.
Two.
7. Amongst the following modes of passage, which one would allow a cell to maintain an
internal environment which is hypertonic relative to its external environment?
a.
b.
c.
d.
Active transport using symporters.
Facilitated diffusion using uniporters.
Transport by group translocation.
Passive diffusion by porins.
8. EMB medium is used in food microbiology to verify for the presence of E. coli based on the
fact that these bacteria ferment lactose. This medium inhibits the growth of Gram positive
bacteria. In addition, colonies of bacteria that ferment lactose are pink whereas those that
do not are colorless. EMB represents what type of medium?
a.
b.
c.
d.
Only selective.
Selective and differential.
Only differential
None of these answers are correct.
9. If bacteria are grown in the presence of a radioactive source of sulfur (35SO4), the
end up in all of the following structures except for which one?
a.
b.
c.
d.
35
S would
The flagella.
The fimbriaes.
The magnetosomes.
The gas vesicles.
10. Which of the following statements about respiration and fermentation is false?
a.
b.
c.
d.
Fermentation and respiration can occur in the presence of oxygen.
Both types of metabolisms involve the oxidation of glucose.
Both types of metabolisms can use inorganic final electron acceptors.
Both types of metabolisms involve the reduction of NAD+.
11. Which of Koch’s postulates could not be applied to mycoplasmas which cause diseases in
cats?
a. The suspected microorganism must be isolated and grown in a pure culture.
b. The microorganism must be present in all cases of the disease but absent from healthy
individuals.
c. Hosts inoculated with the microorganism, must develop the disease.
d. The same microorganism must be reisolated from the diseased host.
12. Which of the following words does not belong to the group?
a.
b.
c.
d.
Peptidoglycan.
Cellulose.
Chitin.
Phospholipid.
13. Which of the following attributes is unique to bacteroides?
a.
b.
c.
d.
Survival in the absence of oxygen.
The presence of hydrocarbons in their membranes.
The lack of a cell wall.
The presence of sphingolipids.
14. Which bacterial group has the greatest number of species which are pathogenic to humans?
a.
b.
c.
d.
The proteobacteria.
The cyanobacteria.
The bacteroids.
The hyperthermophiles.
15. A antibiotic that inhibits the synthesis of diaminopimelic acid would be effective against
which of the following bacteria?
a.
b.
c.
d.
Streptococcus mitis
Neisseria gonorrhoeae
Clostridium tetani
Stapylococcus aureus
16. The antibiotic described in the previous question would have a maximal efficacy in which of
the following scenarios?
a.
b.
c.
d.
Actively growing bacteria in an isotonic medium.
Bacteria which have stopped growing in an isotonic medium.
Actively growing bacteria in a hypotonic medium.
Actively growing bacteria in a hypertonic medium.
17. What is the nutritional classification of the cyanobacteria?
a.
b.
c.
d.
Autotroph photolithotrophs.
Autotroph chemiolithotrophs.
Heterotroph photoorganotrophs.
Heterotrophes chemioorganotrophs.
18. The internal aw of a cell surviving in which of the following environments would be the
lowest?
a.
b.
c.
d.
Tap water.
Sea water.
Blood.
powdered sugar.
19. Two organotrophic microbes use the same electron source, but derive different quantities of
energy from these. Which of the following statements is therefore true?
a.
b.
c.
d.
The microbe which uses the most oxidize electron acceptor must obtain the most energy.
Both microbes must be anaerobes.
Both microbes use an inorganic final electron acceptor.
The microbe which generates the least energy must use oxygen as a final electron acceptor.
20. Bacteria of the genus Bacillus can be found in a wide variety of environments including soil,
water and the human body. However, bacteria of the genus Chlamydia are obligate
parasites which can only grow in mammalian cells. What can you conclude about the
nutritional needs of these bacterial genera?
a.
b.
c.
d.
The biosynthetic capacity of Chlamydiae must be greater than that of the Bacillus.
The nutritional requirements of the Chlamydiae must be greater than those of the Bacillus.
The Chlamydiae must possess a greater number of biosynthetic enzymes than the Bacillus.
The Chlamydiae must have more enzymes that carry out catabolism than the Bacillus.
21. A new bacterium was discovered and named in honor of the researcher who discovered it.
Which of the following nomenclatures is incorrect?
a.
b.
c.
d.
J. bassis
Johnius bassis
Johnius Bassis
Johnius
22. Which of the following characteristics is not common to both mycoplasmas and
mycobacteria?
a.
b.
c.
d.
A plasma membrane with integral proteins.
The use of membrane transporters.
A metabolism.
The synthesis of ATP in their plasma membranes.
23. These images represent colonies from different strauins of the
same bacterial species. Bacteria «A» and bacteria «B» must
belong to different...?
a.
b.
c.
d.
A
B
Biotypes
Morphotypes
Serotypes
Clonotypes
24. According to the following two oxidoreduction reactions AH + B + ADP → A + BH + ATP »
and « BH + C + ATP → B + CH + ADP», which statement (s) must be true?
a.
b.
c.
d.
Compound «A» has a redox potential which is more positive than that of compound «B».
Compound «A» has a redox potential that is more negative than that of compound «C».
Compound «B» has a redox potential that is more positive than that of compound «C».
b et c.
25. This table presents the hybridization results obtained between
the genomes of three bacteria. Which bacteria probably
represent different strains from different biotypes?
a.
b.
c.
d.
A and B
A and C
B and C
A, B and C
A
B
C
% d'hybrids
A
B
99% 5%
5%
99%
85% 12%
C
85%
12%
99%
Part 2. Answer ONLY 3 of the 4 questions, or else only the first three which have been
answered will be corrected. (5 points/question)
1. Match each of the terms in list « A » with the most appropriate term from list « B ». Each
term from list « B » can only be used once.
List A
List B
M
Miasma.
A.
Methanogen
K
G:C percentage.
B.
pH
C
Osmotic pressure.
C.
Compatible solute
N
Serotype.
D.
Acetaldehyde
E.
Mycoplasma
F.
Phagocytosis
G.
Motility
H.
Archeobacteria
I.
Lactic acid
J.
Louis Pasteur
K.
Melting point
L.
Mycobacterium
T/H/P Cell wall lacking peptidoglycan.
O
Syphilis.
G
Cytoskeleton.
H
Extreme thermophile.
R
L
Discovery of human pathogens.
Diagnostic staining for leprosy.
S
SYTOX
F
Extracellular polysaccharide
M.
Diseases
A
Hydrogen gas
N.
Antiserum
D/T
Ethanolic fermentation
O.
Spirochetes
B
Antiporter
P.
Chlamydia
Q.
Bacteroids
R.
Robert Koch
S.
DAPI
T.
Yeast
2a. Respiration is a metabolic process that involves « A » of glucose generating two molecules
of pyruvate. The electrons obtained by thei process are used to « B » 2 molecules of the
electron carrier « C ». These electron carriers are regenerated by giving their electrons to to
a final acceptor « D » whose redox potential is more « E ». This is in contrast to
fermentation which involves the transfer of electrons to a final electron acceptor that is « F ».
Alternatively, microorganisms such as the cyanoobacteria, use a process of « G » « H »
which involves the « I » of a « J » compound and the « K » electron accepting pigment. The
redox potential of the pigment is then made more « L » by using the energy from light.
Indicate the number than coressponds to the appropriate word in each of the blanks
in the table below. Each word can be used more than once.
1. Anoxygenic
2. Chemosynthesis
3. Inorganic
4. NAD+
5. NADH
6. Negative
7. Organic
8. Oxidation
9. Oxygenic
10. Positive
11. Photosynthesis
12. Reduction
A. 8
B. 12
C. 4
D. 3
E. 10
F. 7
G. 11
H. 9
I.
J. 3
K. 12
L. 6
8
2b. What would be the consequence of being unable to regenerate the reducing equivalents
used for energy metabolism? (Maximum of two sentences)
NAD+ would be exhausted and thus glycolysis and the Kreb’s cycle could not continue. There
would be no way to generate energy.
3. The following graphs illustrate the transport of an amino acid (aa1). Graph I presents the
change in the ratio between the internal and external concentrations of aa1 as a function of
time. At the time indicated by the arrow, a second amino acid (aa2) was added. Graph II
shows the transport rate of aa1 as a function of the external concentration of aa1 in the
presence or absence of d’aa2.
II
1.0
+ aa2
Taux
Internal Concentration of aa1
External concentration of aa1
I
2.0
0.5
0.2
+ aa2
0.1
Time
without aa2
Concentration of aa1
3a. Indicate the possible type (s) of transport of aa1 occurring before the addition of aa2.
Passive diffusion
3b. Indicate the possible type (s) of transport of aa1 occurring after the addition of aa2.
Facilitated diffusion.
3c. Indicate the possible type (s) of transporters involved before the addition of aa2.
None
3d. Indicate the possible type (s) of transporters involved after the addition of aa2.
Symporter
Cell wall and gram staining :
4a. What color would Salmonella typhimurium and Clostridium tetani, which were initially
treated with a detergent, be following a typical Gram stain?
Salmonella: Purple
Clostridium: Purple
4b. What color would cells of Neisseria mucosa and Staphylococcus aureus, which were
initially treated with lysozyme in an isotonic solution, be following a typical gram stain?
Neisseria: Red
Staphylococcus: Red
4c. Gram stains of old cultures of Bacillus are often erronous and appear Gram negative. Give
a possible reason that would explain this. (Maximum of two sentences)
The cell wall is damaged and can no longer retain the iodine crystal violet complex
4d. A researcher created a bacteria lacking a membrane but which has a peptidoglycan based
cell wall similar to that of gram positive bacteria. Give two reasons why these bacteria
would not be viable. (Two sentences)
The following processes could not occur:
Control of pH
Excretion of waste products
Synthesis of ATP
Maintaining an internal Aw
Nutrient transport