Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses chemical compounds as an energy source and organic compounds as a carbon source.

Question 2

A microbiologist observes a bacterial culture that only grows at the bottom of a thioglycollate broth tube. Which term best describes this organism?

Accepted Answer

Obligate anaerobe

Question 3

Which toxic form of oxygen is produced during aerobic metabolism and is detoxified by the enzyme catalase?

Accepted Answer

Peroxide anion

Question 4

A bacterium isolated from a hot spring grows optimally at 70°C. Which category does this organism belong to?

Accepted Answer

Thermophile

Question 5

Which of the following best explains why nitrogen fixation is essential for life on Earth?

Accepted Answer

It converts atmospheric nitrogen into a form usable by living organisms.

Question 6

Which of the following is a correct description of a biofilm?

Accepted Answer

A complex community of microorganisms attached to a surface and encased in an extracellular matrix.

Question 7

A bacterium is found to grow equally well throughout a thioglycollate broth tube. Which oxygen requirement classification does it fit?

Accepted Answer

Aerotolerant anaerobe

Question 8

Which of the following best describes the effect of temperature on the growth rate of a typical mesophile?

Accepted Answer

Growth rate increases with temperature up to an optimum, then rapidly decreases at higher temperatures.

Question 9

Which of the following media would you use to isolate a bacterium that can ferment lactose from a mixed culture?

Accepted Answer

MacConkey agar

Question 10

A microbiologist wants to estimate the number of viable bacteria in a water sample. Which method should they use?

Accepted Answer

Serial dilution and viable plate count

Question 11

Which equation correctly represents the calculation of generation time ($$g) if $$the number of cells doubles every $$t$$ minutes?

Accepted Answer

$$g = \frac{t}{n}$$, where $$n is $$the number of generations

Question 12

Which of the following best describes an enrichment culture?

Accepted Answer

A culture technique that favors the growth of a particular microorganism over others.

Question 13

Which of the following is NOT a direct method for measuring microbial growth?

Accepted Answer

Turbidity measurement

Question 14

A bacterium is isolated from a salt lake and requires high salt concentrations for growth. What is the best term for this organism?

Accepted Answer

Obligate halophile

Question 15

Which of the following statements about the stationary phase of a bacterial growth curve is correct?

Accepted Answer

The number of new cells equals the number of dying cells.

Question 16

Which of the following best explains why endospores can survive in dry environments?

Accepted Answer

They cease most metabolic activity and retain water within their structure.

Question 17

A microbiologist uses a spectrophotometer to measure the turbidity of a bacterial culture. What is being measured?

Accepted Answer

The amount of light scattered by the culture

Question 18

Which of the following is a growth factor?

Accepted Answer

A vitamin that cannot be synthesized by the organism

Question 19

Which of the following best describes the function of a selective medium?

Accepted Answer

It supports the growth of only certain types of microorganisms while inhibiting others.

Question 20

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

Accepted Answer

Use of a GasPak anaerobic system

Microbial Nutrition, Growth, and Culturing: Study Notes

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