Question 1

Which of the following best describes the difference between a pure culture and a biofilm?

Accepted Answer

A pure culture contains only one species of microbe, while a biofilm is a mixed community of microbes living together.

Question 2

A microbiologist is culturing a thermophile. Which temperature range should she use for optimal growth?

Accepted Answer

$$50-65^\circ C$$

Question 3

Which phase of the bacterial growth curve is characterized by a balance between cell division and cell death?

Accepted Answer

Stationary phase

Question 4

A sample contains both obligate anaerobes and facultative anaerobes. If exposed to oxygen, what is the expected outcome?

Accepted Answer

Obligate anaerobes will die, while facultative anaerobes will survive and grow.

Question 5

Which of the following media types would you use to isolate only Staphylococcus aureus from a mixed sample?

Accepted Answer

Selective media

Question 6

Which method is most appropriate for sterilizing heat-sensitive liquids, such as vaccines?

Accepted Answer

Filtration

Question 7

A researcher wants to reduce the number of microbes on living tissue before surgery. Which process should she use?

Accepted Answer

Antisepsis

Question 8

Which of the following statements about endospores is correct?

Accepted Answer

Endospores are highly resistant and require autoclaving or sporicides for destruction.

Question 9

Which equation correctly represents the exponential growth of bacteria during the log phase?

Accepted Answer

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

Question 10

A food company wants to reduce pathogens in milk without sterilizing it. Which process should they use?

Accepted Answer

Pasteurization

Question 11

Which type of microbe would be most likely to survive in a highly acidic environment (pH 1-5)?

Accepted Answer

Acidophiles

Question 12

A hospital is trying to eliminate prions from surgical instruments. Which statement is most accurate?

Accepted Answer

Prions are very resistant and require extra harsh sterilization methods.

Question 13

Which of the following is a direct method for counting microbes?

Accepted Answer

Flow cytometry

Question 14

Which of the following statements about autotrophs is correct?

Accepted Answer

Autotrophs make their own carbon from $$CO_2.$$

Question 15

Which physical control method is most effective for killing all microbes, including endospores?

Accepted Answer

Autoclaving (steam + pressure)

Question 16

A scientist is studying a microbe that grows best at $$-5^\circ C. $$What is the classification of this microbe?

Accepted Answer

Psychrophile

Question 17

Which of the following is a chemical method for microbial control that damages DNA?

Accepted Answer

Non-ionizing UV radiation

Question 18

Which type of microbe would be most likely to survive in Dead Sea salt concentrations?

Accepted Answer

Halophiles

Question 19

A patient is infected with Mycobacterium tuberculosis. Which statement about its control is correct?

Accepted Answer

It is hard to kill due to its waxy coat.

Question 20

Which of the following best describes the difference between phototrophs and chemotrophs?

Accepted Answer

Phototrophs use light for energy, while chemotrophs use chemicals.

Microbial Growth and Control – Study Guide

Study Guide - Practice Questions