Q: Which equation correctly calculates the generation time ($$g) $$for a bacterial culture?

$$g = \frac{\text{total time (min)}}{\text{number of generations}}$$

Q: Which of the following equations correctly represents the calculation of colony-forming units (CFU) per milliliter in a viable plate count?

$$\text{CFU/mL} = \frac{\text{number of colonies}}{\text{dilution factor} \times \text{volume plated (mL)}}$$

Question 1

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

A process where a parent cell divides into two genetically identical daughter cells after chromosome replication

Question 2

A microbiologist wants to maintain a bacterial culture in the log phase for maximum product yield. Which system should be used?

Accepted Answer

Chemostat

Question 3

Which equation correctly calculates the generation time ($$g) $$for a bacterial culture?

Accepted Answer

$$g = \frac{	ext{total time (min)}}{	ext{number of generations}}$$

Question 4

Which of the following best explains why biofilms are a major concern in healthcare settings?

Accepted Answer

Biofilms are difficult to treat and contribute to persistent infections

Question 5

A bacterium isolated from a hot spring grows optimally at 70°C. How would you classify this organism?

Accepted Answer

Thermophile

Question 6

Which of the following statements about halophiles is correct?

Accepted Answer

They maintain high concentrations of organic materials and ions to prevent plasmolysis

Question 7

Which enzyme is responsible for converting superoxide ions ($$O_2$$^-$$) to hydrogen peroxide (H_2O_2$) in aerobic bacteria?

Accepted Answer

Superoxide dismutase

Question 8

A culture medium contains 10 grams of tryptone, 5 grams of yeast extract, and 10 grams of NaCl per liter. Which type of medium is this?

Accepted Answer

Complex (enriched) medium

Question 9

Which of the following best describes a fastidious microbe?

Accepted Answer

A microbe that requires multiple growth factors supplied in the medium

Question 10

Which of the following is a correct pairing of a germicide and its classification?

Accepted Answer

Hydrogen peroxide – High-level germicide at high concentrations

Question 11

A microbiologist wants to enumerate only living bacterial cells in a sample. Which method should be used?

Accepted Answer

Viable plate count

Question 12

Which of the following best explains why boiling is not a reliable method for sterilization?

Accepted Answer

Boiling does not kill endospores

Question 13

Which of the following equations correctly represents the calculation of colony-forming units (CFU) per milliliter in a viable plate count?

Accepted Answer

$$	ext{CFU/mL} = \frac{	ext{number of colonies}}{	ext{dilution factor} 	imes 	ext{volume plated (mL)}}$$

Question 14

Which of the following control methods is most effective for eliminating prions from surgical instruments?

Accepted Answer

A combination of chemical treatments and increased temperature and pressure during autoclaving

Question 15

A clinical sample is collected for anaerobic culture. Which of the following is essential to prevent the death of obligate anaerobes before culturing?

Accepted Answer

Quickly sealing the sample in specialized anaerobic transport media

Question 16

Which of the following best describes the action of UV (ultraviolet) radiation on microbial cells?

Accepted Answer

It causes thymine dimers in DNA, leading to mutations

Question 17

Which of the following is a key difference between selective and differential media?

Accepted Answer

Selective media foster the growth of certain microbes and suppress others, while differential media visually distinguish between different microbes

Question 18

Which of the following best explains why Mycobacterium tuberculosis is difficult to control with standard disinfectants?

Accepted Answer

Its cell wall contains waxy mycolic acids that protect it from many chemicals

Question 19

A patient sample is streaked on mannitol salt agar (MSA). Which result would indicate the presence of Staphylococcus aureus?

Accepted Answer

Growth with yellow colonies, indicating mannitol fermentation

Question 20

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

Accepted Answer

Sterilization eliminates all microbes including endospores, while disinfection reduces microbial numbers but may not eliminate all pathogens or endospores

Chapter 7 Fundamentals of Microbial Growth and Decontamination

Study Guide - Practice Questions

Study Guide - Flashcards