BIOL 401 – General Microbiology
Due Sept. 10, 2008
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Problem Set 1
Please use Scantron Form No. 882-E to answer questions 1-15. (Do not wrinkle or attach the
Scantron form.) For questions 16-22, write clearly; if the answer is not legible, it will be marked as
incorrect.
1. The presence of ____________ on Mars today would increase the chance that microbial life exists there.
(A) liquid water
(B) oxygen
(C) nitrogen gas
(D) ammonia
(E) DNA
2. The first genomes to be sequenced were those of
(A) humans
(C) viruses
(E) fungi
(B) bacteria
(D) prions
3. The environment of early Earth most likely contained all of the following EXCEPT
(A) ferrous iron
(B) methane
(C) ammonia
(D) oxygen
(E) hydrogen gas
4. Which microbes may resemble those of the earliest life forms?
(A) archaea
(B) photosynthetic microbes
(C) viruses
(D) cyanobacteria
(E) protists
5. Early metabolism may have been catalyzed by
(A) DNA
(C) protein
(E) carbohydrates
(B) RNA
(D) amino acids
6. The first person to visualize individual microbes was
(A) Antoni van Leeuwenhoek
(B) Robert Hooke
(C) Louis Pasteur
(D) Robert Koch
(E) Edward Jenner
7. Barely __ % of all microbial species can be cultured in the laboratory.
(A) 50
(B) 25
(C) 10
(D) 1
(E) 0.1
8. In the three-domain model, the bacterial ancestor of mitochondria derives from ancient
(A) fungi
(B) cyanobacteria
(C) proteobacteria
(D) archaea
(E) protists
9. Atomic force microscopy measures ____________ between a probe and an object to map the threedimensional topography of a cell.
(A) hydrogen bonds
(B) covalent interactions
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Problem Set 1 - Page 1 of 3
BIOL 401 – General Microbiology
(C) van der Waals forces
(E) magnetic interactions
Due Sept. 10, 2008
(D) pH changes
10. When two waves are out of phase by ____________ wavelength, they produce destructive interference,
canceling each other’s amplitude and resulting in contrast in the image.
(A) one-tenth
(B) one-eighth
(C) one-quarter
(D) one-half
(E) one
11. Which is the counterstain in the Gram stain procedure?
(A) crystal violet
(B) methylene blue
(C) malachite green
(D) safranin
(E) Gram’s iodine
12. Which of the following is a true statement about Gram staining?
(A) The Gram stain differentiates between the three domains.
(B) In a gram-negative cell, the crystal violet-iodide complex is retained by multiple layers of
peptidoglycan.
(C) The outer membrane is disrupted by the decolorizer.
(D) Human cells appear gram-positive.
(E) The mordant is used so that gram-negative cells may be observed.
13. Observations of bacterial flagella during motility are best suited to
(A) bright-field microscopy
(B) dark-field microscopy
(C) SEM
(D) TEM
(E) NMR
14. In fluorescence microscopy, incident light is absorbed by the specimen and reemitted at a ____________
energy, resulting in a ____________.
(A) lower, longer wavelength
(B) lower, shorter wavelength
(C) higher, longer wavelength
(D) higher, shorter wavelength
(E) higher, higher contrast
15. The aromatic groups of the fluorophore DAPI associate exclusively with the
(A) cell wall.
(B) base pairs of DNA.
(C) flagella.
(D) cell membrane.
(E) pili.
16 Fill in the blanks below.
12 nm = ____________________________________ mm.
36 μm = ____________________________________ nm.
17. How would you argue that a virus is a living organism? What are some counter-arguments?
18. You are trying to fulfill the criteria of Koch’s postulates to establish a causative link between a microbe
and a disease. You have isolated a microbe from a diseased host and grown it in pure culture, but when
you introduce the microbe into a healthy host, no disease occurs. Provide some possible explanations.
19. Why should Archaea be classified as a third domain of life?
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Problem Set 1 - Page 2 of 3
BIOL 401 – General Microbiology
Due Sept. 10, 2008
20 What is the numerical aperture of an air lens with an angle of aperture of 60°? What does the angle of
aperture of an air lens have to be in order for its numerical aperture to equal 1.2?
21. Why are stains used in microscopy? Compare and contrast the stains used in light versus electron
microscopy.
22. Give reasons why SEM and TEM cannot be used to observe living specimen.
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Problem Set 1 - Page 3 of 3