DIF: Medium REF: 1.3 TOP: III.C.iii MSC: Understanding
12. How would you use Robert Koch’s postulates to prove that a specific organism causes a new disease
in mice?
ANS:
See Figure 1.18 in the textbook.
(1) The suspected organism is found in all diseased mice, but is absent from healthy mice.
(2) The suspected organism is isolated from the diseased mice and grown in pure culture.
(3) When the suspected organism is introduced into a healthy mouse, the same disease occurs.
(4) The same strain of microbe is obtained from the newly diseased mouse.
DIF: Medium REF: 1.3 TOP: III.B.ii MSC: Applying
13. Explain why the organisms that were studied by Sergei Winogradsky could not be grown on Robert
Koch’s plate media containing agar or gelatin.
ANS:
The organisms studied by Winogradsky were lithotrophs, which feed solely on inorganic substances.
Koch’s plate media contained organic nutrient sources.
DIF: Difficult REF: 1.4 TOP: IV.A.ii MSC: Understanding
14. Is it true that only culturable bacteria contribute to ecology? Explain your answer.
ANS:
No, this is not a true statement. It is estimated that barely 0.1% of microbial species can be cultured.
The work of Winogradsky and later microbial ecologists showed that bacteria are necessary for
geochemical cycling. Many of these organisms can’t be grown in pure culture on laboratory media, but
can be grown in enrichment culture such as a Winogradsky column.
DIF: Difficult REF: 1.4 TOP: IV.B MSC: Understanding
15. Define the term ―endosymbiont‖ and give an example of an endosymbiotic relationship found in
nature.
ANS:
An endosymbiont is an organism living symbiotically inside a larger organism. Examples may vary,
but include the following: Rhizobium in a leguminous plant; bioluminescent bacteria in the light
organs of fish and squid; photosynthetic algae and coral.
DIF: Medium REF: 1.4 TOP: IV.B MSC: Applying
16. Give two reasons why microbes have been difficult to classify.
ANS:
First, even with the use of light microscopes, only the basic shape of microbes can be determined, and
many microbes have similar shapes even though they are very different in other ways. Second,
microbes do not fit the classic definition of a species, which is a group of organisms that interbreed.
Microbes typically reproduce asexually. When they do exchange genes, they may do so with distantly
related species.
DIF: Medium REF: 1.5 TOP: V.A.i | V.A.ii
, MSC: Understanding
17. Briefly explain the endosymbiosis theory and the evidence that supports it.
ANS:
The endosymbiosis theory proposes that mitochondria and chloroplasts evolved from bacteria that
were engulfed by pre-eukaryotic cells, and that over time these endosymbiotic prokaryotic cells lost
the ability to survive outside of the host cell but were maintained as organelles. Evidence supporting
the endosymbiosis theory includes the fact that mitochondria and chloroplasts possess circular DNA
with similarity to modern bacteria.
DIF: Difficult REF: 1.5 TOP: V.C MSC: Understanding
18. What were the contributions of Rosalind Franklin toward discovering the structure of DNA and why
wasn’t she one of the recipients of the Nobel Prize for this discovery?
ANS:
She was an X-ray crystallographer who studied the structure of DNA. Her X-ray micrographs showed
for the first time that DNA was a double helix. A colleague showed her micrographs to James Watson,
who was also studying the structure of DNA. Watson and Francis Crick published their model of the
structure of DNA in the journal Nature and denied that they had used Franklin’s micrographs.
DIF: Medium REF: 1.6 TOP: VI.C.i MSC: Remembering
19. Briefly describe how the ultracentrifuge is used to determine the sizes of cellular macromolecules.
ANS:
The ultracentrifuge uses centrifugal forces to separate cell components. Theodor Svedberg calculated
that the particle sizes could be determined based on the rate of sedimentation of the particles in an
ultracentrifuge.
DIF: Medium REF: 1.6 TOP: VI.B.ii MSC: Understanding
20. If you want to produce DNA polymerases like those used in polymerase chain reaction (PCR) for
amplification of DNA, from which natural environment would you try to isolate the producers?
ANS:
Taq DNA polymerase used in PCR amplification of DNA was extracted from Thermus aquaticus, a
bacterium found in a hot spring in Yellowstone National Park. Since DNA polymerase has to survive
many rounds of cycling to near-boiling temperatures, the most conducive environment for finding
DNA polymerase, such as the enzymes used in PCR reactions, would be searching for microbes in an
environment where the temperature is extremely high.
DIF: Difficult REF: 1.6 TOP: VI.C.ii MSC: Applying
,CHAPTER 2: Observing the Microbial Cell
MULTIPLE CHOICE
1. Who proved that stomach ulcers are caused by a bacterium?
a. Hooke d. Jenner
b. Marshall e. van Leeuwenhoek
c. Gram
ANS: B DIF: Easy REF: Introduction TOP: VI
MSC: Remembering
2. The part of the human eye that is most involved in resolving an image is the:
a. iris d. retina
b. lens e. cornea
c. optic nerve
ANS: D DIF: Medium REF: 2.1 TOP: I.A
MSC: Remembering
3. A ball-shaped microbe is referred to as a:
a. bacillus d. strepto
b. coccus e. spirochete
c. vibrio
ANS: B DIF: Easy REF: 2.1 TOP: I.C.ii.b
MSC: Remembering
4. Resolution is the smallest distance by which two objects can be and still be .
a. magnified; seen d. distinguished; separated
b. separated; distinguished e. magnified; distinguished
c. magnified; separated
ANS: B DIF: Medium REF: 2.1 TOP: I.A.i
MSC: Understanding
5. 400 nm is equivalent to:
a. 4.0 x 10-5 m d. 4.0 x 10-8 m
b. 4.0 x 10-6 m e. 4.0 x 10-9 m
c. 4.0 x 10-7 m
ANS: C DIF: Medium REF: 2.1 TOP: I.A
MSC: Applying
6. Which of these series arranges microbes from smallest to largest?
a. virus → bacterium → red blood cell → paramecium
b. virus → red blood cell → bacterium → paramecium
c. bacterium → virus → paramecium → red blood cell
d. bacterium → virus → red blood cell → paramecium
e. paramecium → red blood cell → bacterium → virus
ANS: A DIF: Difficult REF: 2.1 TOP: I.C
MSC: Applying
, 7. The heating of water when exposed to light is primarily due to:
a. reflection d. scattering
b. refraction e. fluorescence
c. absorption
ANS: C DIF: Difficult REF: 2.2 TOP: II.B.i.a
MSC: Remembering
8. Wavelength interference results in small observed objects (like bacteria) being surrounded by:
a. a capsule d. a dark field
b. a membrane e. a cell wall
c. an Airy disk
ANS: C DIF: Medium REF: 2.2 TOP: II.C
MSC: Remembering
9. What is the most important property that enables a lens to magnify an image?
a. absorption d. refraction
b. fluorescence e. scattering
c. reflection
ANS: D DIF: Medium REF: 2.2 TOP: II.C
MSC: Understanding
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 of a d. one-half of a
b. one-eighth of a e. one
c. one-quarter of a
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
11. Increasing the refractive index of the medium between the object and the objective lens increases:
a. refraction d. resolution
b. reflection e. wavelength
c. magnification
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
12. If a glass slide was submerged in a beaker of immersion oil, the slide would be:
a. undetectable d. fluorescent
b. brighter than its surroundings e. stained
c. darker than its surroundings
ANS: A DIF: Medium REF: 2.2 TOP: II.A.ii.a
MSC: Applying
13. What would happen if a lens had the same refractive index as air?
a. Light would not pass through the lens.
b. The image would be magnified more than with a glass lens.
c. The image would be magnified, but the resolution would be less than with a glass lens.
d. The image would be magnified, and the resolution would be greater than with a glass lens.
e. The image would not be magnified.
12. How would you use Robert Koch’s postulates to prove that a specific organism causes a new disease
in mice?
ANS:
See Figure 1.18 in the textbook.
(1) The suspected organism is found in all diseased mice, but is absent from healthy mice.
(2) The suspected organism is isolated from the diseased mice and grown in pure culture.
(3) When the suspected organism is introduced into a healthy mouse, the same disease occurs.
(4) The same strain of microbe is obtained from the newly diseased mouse.
DIF: Medium REF: 1.3 TOP: III.B.ii MSC: Applying
13. Explain why the organisms that were studied by Sergei Winogradsky could not be grown on Robert
Koch’s plate media containing agar or gelatin.
ANS:
The organisms studied by Winogradsky were lithotrophs, which feed solely on inorganic substances.
Koch’s plate media contained organic nutrient sources.
DIF: Difficult REF: 1.4 TOP: IV.A.ii MSC: Understanding
14. Is it true that only culturable bacteria contribute to ecology? Explain your answer.
ANS:
No, this is not a true statement. It is estimated that barely 0.1% of microbial species can be cultured.
The work of Winogradsky and later microbial ecologists showed that bacteria are necessary for
geochemical cycling. Many of these organisms can’t be grown in pure culture on laboratory media, but
can be grown in enrichment culture such as a Winogradsky column.
DIF: Difficult REF: 1.4 TOP: IV.B MSC: Understanding
15. Define the term ―endosymbiont‖ and give an example of an endosymbiotic relationship found in
nature.
ANS:
An endosymbiont is an organism living symbiotically inside a larger organism. Examples may vary,
but include the following: Rhizobium in a leguminous plant; bioluminescent bacteria in the light
organs of fish and squid; photosynthetic algae and coral.
DIF: Medium REF: 1.4 TOP: IV.B MSC: Applying
16. Give two reasons why microbes have been difficult to classify.
ANS:
First, even with the use of light microscopes, only the basic shape of microbes can be determined, and
many microbes have similar shapes even though they are very different in other ways. Second,
microbes do not fit the classic definition of a species, which is a group of organisms that interbreed.
Microbes typically reproduce asexually. When they do exchange genes, they may do so with distantly
related species.
DIF: Medium REF: 1.5 TOP: V.A.i | V.A.ii
, MSC: Understanding
17. Briefly explain the endosymbiosis theory and the evidence that supports it.
ANS:
The endosymbiosis theory proposes that mitochondria and chloroplasts evolved from bacteria that
were engulfed by pre-eukaryotic cells, and that over time these endosymbiotic prokaryotic cells lost
the ability to survive outside of the host cell but were maintained as organelles. Evidence supporting
the endosymbiosis theory includes the fact that mitochondria and chloroplasts possess circular DNA
with similarity to modern bacteria.
DIF: Difficult REF: 1.5 TOP: V.C MSC: Understanding
18. What were the contributions of Rosalind Franklin toward discovering the structure of DNA and why
wasn’t she one of the recipients of the Nobel Prize for this discovery?
ANS:
She was an X-ray crystallographer who studied the structure of DNA. Her X-ray micrographs showed
for the first time that DNA was a double helix. A colleague showed her micrographs to James Watson,
who was also studying the structure of DNA. Watson and Francis Crick published their model of the
structure of DNA in the journal Nature and denied that they had used Franklin’s micrographs.
DIF: Medium REF: 1.6 TOP: VI.C.i MSC: Remembering
19. Briefly describe how the ultracentrifuge is used to determine the sizes of cellular macromolecules.
ANS:
The ultracentrifuge uses centrifugal forces to separate cell components. Theodor Svedberg calculated
that the particle sizes could be determined based on the rate of sedimentation of the particles in an
ultracentrifuge.
DIF: Medium REF: 1.6 TOP: VI.B.ii MSC: Understanding
20. If you want to produce DNA polymerases like those used in polymerase chain reaction (PCR) for
amplification of DNA, from which natural environment would you try to isolate the producers?
ANS:
Taq DNA polymerase used in PCR amplification of DNA was extracted from Thermus aquaticus, a
bacterium found in a hot spring in Yellowstone National Park. Since DNA polymerase has to survive
many rounds of cycling to near-boiling temperatures, the most conducive environment for finding
DNA polymerase, such as the enzymes used in PCR reactions, would be searching for microbes in an
environment where the temperature is extremely high.
DIF: Difficult REF: 1.6 TOP: VI.C.ii MSC: Applying
,CHAPTER 2: Observing the Microbial Cell
MULTIPLE CHOICE
1. Who proved that stomach ulcers are caused by a bacterium?
a. Hooke d. Jenner
b. Marshall e. van Leeuwenhoek
c. Gram
ANS: B DIF: Easy REF: Introduction TOP: VI
MSC: Remembering
2. The part of the human eye that is most involved in resolving an image is the:
a. iris d. retina
b. lens e. cornea
c. optic nerve
ANS: D DIF: Medium REF: 2.1 TOP: I.A
MSC: Remembering
3. A ball-shaped microbe is referred to as a:
a. bacillus d. strepto
b. coccus e. spirochete
c. vibrio
ANS: B DIF: Easy REF: 2.1 TOP: I.C.ii.b
MSC: Remembering
4. Resolution is the smallest distance by which two objects can be and still be .
a. magnified; seen d. distinguished; separated
b. separated; distinguished e. magnified; distinguished
c. magnified; separated
ANS: B DIF: Medium REF: 2.1 TOP: I.A.i
MSC: Understanding
5. 400 nm is equivalent to:
a. 4.0 x 10-5 m d. 4.0 x 10-8 m
b. 4.0 x 10-6 m e. 4.0 x 10-9 m
c. 4.0 x 10-7 m
ANS: C DIF: Medium REF: 2.1 TOP: I.A
MSC: Applying
6. Which of these series arranges microbes from smallest to largest?
a. virus → bacterium → red blood cell → paramecium
b. virus → red blood cell → bacterium → paramecium
c. bacterium → virus → paramecium → red blood cell
d. bacterium → virus → red blood cell → paramecium
e. paramecium → red blood cell → bacterium → virus
ANS: A DIF: Difficult REF: 2.1 TOP: I.C
MSC: Applying
, 7. The heating of water when exposed to light is primarily due to:
a. reflection d. scattering
b. refraction e. fluorescence
c. absorption
ANS: C DIF: Difficult REF: 2.2 TOP: II.B.i.a
MSC: Remembering
8. Wavelength interference results in small observed objects (like bacteria) being surrounded by:
a. a capsule d. a dark field
b. a membrane e. a cell wall
c. an Airy disk
ANS: C DIF: Medium REF: 2.2 TOP: II.C
MSC: Remembering
9. What is the most important property that enables a lens to magnify an image?
a. absorption d. refraction
b. fluorescence e. scattering
c. reflection
ANS: D DIF: Medium REF: 2.2 TOP: II.C
MSC: Understanding
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 of a d. one-half of a
b. one-eighth of a e. one
c. one-quarter of a
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
11. Increasing the refractive index of the medium between the object and the objective lens increases:
a. refraction d. resolution
b. reflection e. wavelength
c. magnification
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
12. If a glass slide was submerged in a beaker of immersion oil, the slide would be:
a. undetectable d. fluorescent
b. brighter than its surroundings e. stained
c. darker than its surroundings
ANS: A DIF: Medium REF: 2.2 TOP: II.A.ii.a
MSC: Applying
13. What would happen if a lens had the same refractive index as air?
a. Light would not pass through the lens.
b. The image would be magnified more than with a glass lens.
c. The image would be magnified, but the resolution would be less than with a glass lens.
d. The image would be magnified, and the resolution would be greater than with a glass lens.
e. The image would not be magnified.
