Question 1

Which of the following best describes a psychrophile?

Accepted Answer

A microorganism that grows optimally at temperatures below $$15\ ^\circ \mathrm{C}$$

Question 2

A food company wants to prevent microbial growth in canned vegetables by adjusting the pH. Which of the following best explains why lowering the pH is effective?

Accepted Answer

Most bacteria cannot survive in acidic environments because their enzymes denature at low pH

Question 3

Which equation correctly represents the exponential growth of bacteria, where $$N is $$the final number of cells, $$N_0 is $$the initial number of cells, $$n is $$the number of generations?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 4

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome?

Accepted Answer

Water will move out of the cell, causing plasmolysis

Question 5

Halophiles are microorganisms that:

Accepted Answer

Require high concentrations of salt for growth

Question 6

Which of the following is a major function of carbon in bacterial cells?

Accepted Answer

It is a primary energy source and building block for macromolecules

Question 7

Nitrogen is essential for bacterial growth because:

Accepted Answer

It is a component of proteins and nucleic acids

Question 8

Which enzyme is responsible for breaking down superoxide radicals ($$O_2$$^-$$) in aerobic bacteria?

Accepted Answer

Superoxide dismutase

Question 9

A facultative anaerobe is grown in a tube of nutrient broth. Where would you expect to see the most growth?

Accepted Answer

Throughout the tube, but more at the top

Question 10

Which of the following best describes a biofilm?

Accepted Answer

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

Question 11

Which of the following is NOT a characteristic of agar?

Accepted Answer

It is digested by most bacteria

Question 12

A selective medium is designed to:

Accepted Answer

Suppress the growth of unwanted microbes and encourage the growth of desired ones

Question 13

Which biosafety level (BSL) is appropriate for handling pathogens that pose a moderate hazard and require limited access and basic PPE?

Accepted Answer

BSL-2

Question 14

Which method is considered a direct measurement of bacterial growth?

Accepted Answer

Plate count

Question 15

A bacterial culture is preserved by freezing at $$-80\ ^\circ \mathrm{C}$$ with glycerol. What is the main purpose of adding glycerol?

Accepted Answer

To prevent ice crystal formation that can damage cells

Question 16

Which of the following best defines a pure culture?

Accepted Answer

A culture containing only one species of microorganism

Question 17

During which phase of bacterial growth is the rate of cell division equal to the rate of cell death?

Accepted Answer

Stationary phase

Question 18

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

Accepted Answer

Plate count after filtration

Question 19

Which of the following is a function of coenzymes in microbial metabolism?

Accepted Answer

They transfer electrons or chemical groups between molecules

Question 20

A bacterial cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

Water will move into the cell, causing it to swell and possibly lyse

Microbial Growth: Environmental and Nutritional Factors, Culture Methods, and Measurement

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