Question 1

Which of the following elements is required in the largest amount for microbial growth, and what is its primary function?

Accepted Answer

Carbon; serves as an energy source and structural molecule

Question 2

A bacterium is classified as a chemoheterotroph. Which of the following best describes its nutritional requirements?

Accepted Answer

Uses organic molecules as both carbon and energy sources

Question 3

Which adaptation would you expect in a psychrophilic bacterium living in Antarctic ice?

Accepted Answer

Membranes rich in unsaturated fatty acids

Question 4

A culture medium contains peptone, beef extract, and yeast extract. Which type of medium is this?

Accepted Answer

Complex medium

Question 5

Which of the following best explains why agar is used as a solidifying agent in culture media?

Accepted Answer

Few microbes can degrade it, and it has favorable melting characteristics

Question 6

A microbiologist wants to isolate Staphylococcus aureus from a mixed culture. Which medium would be most appropriate?

Accepted Answer

Mannitol Salt Agar, which is both selective and differential

Question 7

Which enzyme is produced by most aerobic and aerotolerant organisms to neutralize superoxide radicals?

Accepted Answer

Superoxide dismutase (SOD)

Question 8

A bacterial culture starts with 50 cells and doubles every 20 minutes. How many cells will there be after 2 hours? Use $$N_t = N_0$ 	imes 2^n.$$

Accepted Answer

3,200 cells

Question 9

Which phase of the bacterial growth curve is characterized by metabolic activity but no increase in cell number?

Accepted Answer

Lag phase

Question 10

Why are biofilms problematic in medical settings?

Accepted Answer

They protect microbes from immune responses and antimicrobials

Question 11

Which of the following is a primary metabolite produced during the log phase of bacterial growth?

Accepted Answer

Vitamins

Question 12

A bacterium grows best at pH 2. Which term best describes this organism?

Accepted Answer

Acidophile

Question 13

Which method would be most appropriate for quickly estimating the number of bacteria in a liquid culture without distinguishing live from dead cells?

Accepted Answer

Turbidity measurement

Question 14

What happens to a bacterial cell placed in a hypertonic environment?

Accepted Answer

It undergoes plasmolysis as water leaves the cell

Question 15

Which temperature group includes most human pathogens?

Accepted Answer

Mesophiles

Question 16

Which of the following best describes the function of enrichment media?

Accepted Answer

Enhances growth of specific bacteria by providing required nutrients or growth factors

Question 17

Which of the following is NOT a direct method for counting bacteria?

Accepted Answer

Turbidity measurement

Question 18

A facultative anaerobe is grown in a tube of solid medium. Where would you expect most growth?

Accepted Answer

Throughout the tube, but more at the top

Question 19

Which of the following is a plausible reason why food preservation methods often involve high salt concentrations?

Accepted Answer

High salt causes plasmolysis, inhibiting microbial growth

Question 20

Which of the following best describes the role of biofilms in bioremediation?

Accepted Answer

Biofilms allow multiple bacteria to cooperate in degrading toxins

Microbial Growth I

Study Guide - Practice Questions