Question 1

Which of the following best describes the lag phase in a closed pure batch system of bacterial growth?

Accepted Answer

Cells are adapting to new environmental conditions and synthesizing necessary enzymes.

Question 2

A bacterium that thrives at pH 2 and is isolated from acidic hot springs is best classified as which of the following?

Accepted Answer

Acidophile

Question 3

Which enzyme is commonly used by oxygen-tolerant organisms to eliminate reactive oxygen species, and what is the reaction it catalyzes?

Accepted Answer

Catalase; $2H_2O_2 \rightarrow 2H_2O + O_2$

Question 4

Which of the following best distinguishes a facultative anaerobe from an obligate anaerobe?

Accepted Answer

Facultative anaerobes can use oxygen for metabolism but can also grow without it, while obligate anaerobes are harmed by oxygen.

Question 5

Which of the following is an example of a selective medium, and what is its purpose?

Accepted Answer

MacConkey agar; it inhibits Gram-positive bacteria and allows Gram-negative bacteria to grow.

Question 6

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

Accepted Answer

Plate count method, because it only counts living cells capable of forming colonies.

Question 7

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all forms of microbial life, including spores, while disinfection eliminates most pathogens but not necessarily spores.

Question 8

A hospital uses autoclaving to process surgical instruments. Which physical method is being employed, and what is the standard condition for this process?

Accepted Answer

Moist heat sterilization; $121^\circ C$ at 15 psi for 15 minutes

Question 9

Which of the following chemical agents is most appropriate for disinfecting a surface contaminated with Mycobacterium tuberculosis, and why?

Accepted Answer

Phenol, because it is effective against mycobacteria due to its lipid solubility.

Question 10

A food processing plant must choose a germicide for equipment sanitation. Which factor is LEAST important to consider?

Accepted Answer

The color of the germicide

Question 11

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

Accepted Answer

Phototrophs use light as an energy source, while heterotrophs obtain energy from organic compounds.

Question 12

A microbiologist is testing a new disinfectant. Which of the following would be the best method to evaluate its effectiveness against bacterial spores?

Accepted Answer

Expose a known concentration of spores to the disinfectant and determine the number of surviving spores by plating and colony counting.

Question 13

Which of the following is a correct example of a psychrophile and its typical environment?

Accepted Answer

Psychrobacter spp.; Arctic sea ice

Question 14

Which of the following statements about microaerophiles is correct?

Accepted Answer

They require oxygen at lower concentrations than is present in the atmosphere.

Question 15

A laboratory is using filtration to sterilize a heat-sensitive solution. What pore size should the filter have to effectively remove bacteria?

Accepted Answer

$0.22\ \mu m$

Question 16

Which of the following best explains why thermophiles can survive at high temperatures?

Accepted Answer

Their proteins and membranes are stabilized by increased hydrogen bonding and saturated fatty acids.

Question 17

Which of the following is a correct definition of decontamination?

Accepted Answer

The mechanical removal of most microbes from a surface to safe levels.

Question 18

A patient with a wound infection is treated with hydrogen peroxide. Which type of microbial control is being used, and what is the mechanism?

Accepted Answer

Antisepsis; hydrogen peroxide produces reactive oxygen species that damage cellular components.

Question 19

Which of the following is a key difference between batch culture and chemostat systems for bacterial growth?

Accepted Answer

Batch culture has a closed system with limited nutrients, while a chemostat maintains continuous nutrient supply and waste removal.

Question 20

Which of the following best describes the action of a bacteriostatic agent?

Accepted Answer

It inhibits the growth and reproduction of bacteria without killing them.

Microbial Growth, Adaptation, and Control: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards