Question 1

Which of the following best describes a chemoautotroph?

Accepted Answer

An organism that uses chemical compounds as an energy source and CO$$_2 as a $$carbon source.

Question 2

A bacterium that can survive in the presence or absence of oxygen, switching between aerobic respiration and fermentation, is best classified as:

Accepted Answer

Facultative anaerobe

Question 3

Which enzyme allows bacteria to break down toxic hydrogen peroxide into water and oxygen?

Accepted Answer

Catalase

Question 4

A microbiologist is culturing bacteria from a deep-sea vent. Which environmental factor is most critical for the survival of these microbes?

Accepted Answer

High hydrostatic pressure

Question 5

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

Accepted Answer

They lack enzymes to detoxify reactive oxygen species.

Question 6

A culture medium that contains substances favoring the growth of one microbe while inhibiting others is called:

Accepted Answer

Selective medium

Question 7

MacConkey agar is used to distinguish between lactose fermenters and non-fermenters among Gram-negative bacteria. This is an example of:

Accepted Answer

Both selective and differential medium

Question 8

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

Accepted Answer

Cells are adapting to new environment and not dividing rapidly.

Question 9

A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours of exponential growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2^6$ = 64$$

Question 10

Which of the following best describes a halophile?

Accepted Answer

An organism that requires high salt concentrations for growth.

Question 11

Why is nitrogen fixation by certain bacteria essential to life on Earth?

Accepted Answer

It converts atmospheric nitrogen into forms usable by living organisms.

Question 12

Which of the following best describes the function of enrichment culture techniques?

Accepted Answer

To increase the number of a specific microbe relative to others in a sample.

Question 13

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

Accepted Answer

Viable plate count

Question 14

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms are complex, multi-species communities that use chemical signals for communication.

Question 15

Which of the following best explains why most bacteria have not been cultured in the laboratory?

Accepted Answer

They require specific nutrients or conditions not provided in standard media.

Question 16

A bacterium that grows best at 70$$^\circC is $$classified as a:

Accepted Answer

Thermophile

Question 17

Which of the following is a direct method for measuring microbial growth?

Accepted Answer

Viable plate count

Question 18

Which of the following best describes a microaerophile?

Accepted Answer

An organism that requires low levels of oxygen.

Question 19

Which of the following is a reason why stationary phase occurs in a bacterial growth curve?

Accepted Answer

Nutrients become limited and waste products accumulate.

Question 20

A researcher wants to distinguish between two bacterial species based on their ability to ferment a specific sugar. Which type of medium should they use?

Accepted Answer

Differential medium

Microbial Nutrition and Growth: Key Concepts and Methods

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