Question 1

Which of the following best describes a psychrophile?

Accepted Answer

A microorganism that grows best at temperatures below 15°C

Question 2

A bacterium isolated from a hot spring in Yellowstone National Park is most likely a(n):

Accepted Answer

Thermophile

Question 3

Which of the following equations correctly calculates the number of generations ($$n) in a $$bacterial culture?

Accepted Answer

$$n = \frac{\log_{10} N_T - \log_{10} N_0$}{0.301}$$

Question 4

Which type of medium would you use to isolate a bacterium that can metabolize a rare sugar, and why?

Accepted Answer

Enrichment medium, because it amplifies the population of bacteria that can use the rare sugar

Question 5

A bacterium that grows only at the bottom of a thioglycolate broth tube is most likely:

Accepted Answer

Obligate anaerobe

Question 6

Which enzyme is responsible for detoxifying hydrogen peroxide in aerobic bacteria?

Accepted Answer

Catalase

Question 7

A microbiologist wants to count only live bacteria in a water sample. Which method should she use?

Accepted Answer

Viable plate count after serial dilution

Question 8

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

They lack the enzymes superoxide dismutase and catalase to detoxify oxygen radicals

Question 9

Which of the following is a chemically defined medium?

Accepted Answer

A medium with known quantities of all ingredients, such as glucose, ammonium sulfate, and magnesium chloride

Question 10

A bacterium that grows equally well throughout a thioglycolate broth tube is most likely a(n):

Accepted Answer

Aerotolerant anaerobe

Question 11

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

The rate of cell division equals the rate of cell death

Question 12

Which of the following is NOT a trace element required by most bacteria?

Accepted Answer

Magnesium (Mg)

Question 13

A bacterium that prefers to grow at pH 9 is classified as a(n):

Accepted Answer

Alkalinophile

Question 14

Which of the following best describes the effect of a hypertonic environment on a bacterial cell?

Accepted Answer

The cell will shrink due to water loss

Question 15

Which of the following media would be most appropriate to distinguish between lactose-fermenting and non-lactose-fermenting bacteria?

Accepted Answer

Differential medium

Question 16

A culture medium that contains sodium chloride to inhibit the growth of most bacteria except halophiles is an example of:

Accepted Answer

Selective medium

Question 17

Which of the following statements about bacterial generation time is correct?

Accepted Answer

It is the time required for a bacterial cell to grow and divide

Question 18

Which of the following is an indirect method for measuring microbial growth?

Accepted Answer

Turbidity measurement using a spectrophotometer

Question 19

A microbiologist wants to culture an obligate anaerobe. Which of the following methods would be most appropriate?

Accepted Answer

Incubation in a gas-pack anaerobic jar

Question 20

Which of the following best explains why a reducing medium is used for culturing anaerobic bacteria?

Accepted Answer

It contains chemicals that remove oxygen from the medium

Microbial Nutrition and Growth: Study Notes

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