Question 1

Which of the following best describes a biofilm and its significance in clinical settings?

Accepted Answer

A biofilm is a complex community of microorganisms attached to a surface, embedded in a self-produced matrix, which increases resistance to antibiotics and disinfectants.

Question 2

If bacterial cells are grown in a medium containing radioactive phosphorus ($$^{32}P$$), where would you expect to find the $$^{32}P $$within the cells?

Accepted Answer

In nucleic acids such as DNA and RNA, and in phospholipids of the cell membrane.

Question 3

Which laboratory biosafety level (BSL) is appropriate for handling agents that are not known to consistently cause disease in healthy adults and present minimal potential hazard?

Accepted Answer

BSL-1

Question 4

Why is sugar added to fruit when making jams and jellies, from a microbiological perspective?

Accepted Answer

Sugar creates a hypertonic environment, causing plasmolysis in microbial cells and inhibiting their growth.

Question 5

A pastry chef accidentally inoculated a cream pie with six $$S. aureus$$ cells. If $$S. aureus$$ has a generation time of 60 minutes, how many cells would be present after 7 hours?

Accepted Answer

$$6 	imes 2^7$ = 768$$ cells

Question 6

Which of the following enzymes is responsible for breaking down hydrogen peroxide ($$H_2O_2) $$into water and oxygen?

Accepted Answer

Catalase

Question 7

What is the main problem with psychrotrophs in food storage?

Accepted Answer

They can grow at low temperatures, such as those in refrigerators, leading to food spoilage.

Question 8

Why do bacteria not grow on beaches contaminated with petroleum oil unless nitrogen and phosphorus are added?

Accepted Answer

Nitrogen and phosphorus are essential nutrients required for bacterial growth and metabolism, which are limited in oil-contaminated environments.

Question 9

Which of the following best explains why refrigeration and freezing preserve foods?

Accepted Answer

Low temperatures slow down or stop microbial metabolism and growth.

Question 10

Which of the following best describes the role of superoxide dismutase in bacterial cells?

Accepted Answer

It converts superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) and oxygen.

Question 11

A microbe is found to grow only at the bottom of a thioglycollate broth tube. What does this indicate about the microbe?

Accepted Answer

It is a strict anaerobe.

Question 12

If you were to measure bacterial growth in a liquid culture using a spectrophotometer, why must you also measure the light transmission of a tube containing only the culture medium?

Accepted Answer

To account for the absorbance of the medium itself, ensuring only bacterial growth is measured.

Question 13

Which of the following best describes the function of peroxidase in bacterial cells?

Accepted Answer

It breaks down hydrogen peroxide using NADH as an electron donor, producing water.

Question 14

Which of the following is a key reason why biofilms are problematic in medical and dental settings?

Accepted Answer

Biofilms protect bacteria from the immune system and increase resistance to antibiotics.

Question 15

Which of the following best explains why Clostridium is killed by oxygen, while Streptococcus (also catalase-negative) is not?

Accepted Answer

Clostridium lacks both catalase and superoxide dismutase, making it unable to detoxify reactive oxygen species.

Question 16

Which of the following best describes the effect of a hypertonic environment on a bacterial cell?

Accepted Answer

Water leaves the cell, causing plasmolysis and inhibiting growth.

Question 17

Which of the following statements about the generation time of bacteria is correct?

Accepted Answer

Generation time is the time required for a bacterial population to double in number.

Question 18

Which of the following best explains why a plate count is preferred over a spectrophotometer for determining the number of viable bacteria in a culture?

Accepted Answer

Plate counts measure only living cells capable of forming colonies.

Question 19

A prokaryotic cell is discovered that is a psychrophile, an obligate halophile, and an obligate aerobe. Based on these characteristics, what can you infer about the planet it came from?

Accepted Answer

The planet likely has cold temperatures, high salt concentrations, and an oxygen-rich atmosphere.

Question 20

Which culture of yeast would produce more ATP: one grown aerobically or one grown anaerobically, and why?

Accepted Answer

Aerobic culture, because aerobic respiration yields more ATP per glucose molecule.

Microbial Growth and Physiology: Chapter 6 Study Guidance

Study Guide - Practice Questions

Study Guide - Flashcards