Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses organic compounds for both energy and carbon.

Question 2

A bacterial culture is in the logarithmic phase of growth. Which of the following is true during this phase?

Accepted Answer

The population is increasing exponentially and cells are most susceptible to antibiotics.

Question 3

Which equation correctly calculates the total number of bacterial cells after a given number of generations?

Accepted Answer

$$N_{total} = (N_{initial})2^n$$

Question 4

A sandwich is contaminated with 10 Staphylococcus aureus cells. If the generation time is 20 minutes and the sandwich is left for 4 hours, how many cells will there be? (Use $$N_{total} = (N_{initial})2^n)$$

Accepted Answer

10,240 cells

Question 5

Which of the following best explains why biofilm-associated infections are difficult to treat?

Accepted Answer

Biofilms provide a protective matrix that shields bacteria from antibiotics and the immune system.

Question 6

Which of the following is NOT a correct pairing of microbe and its optimal temperature range?

Accepted Answer

Hyperthermophile – optimal growth at 10–20$$^\circC$$

Question 7

Which of the following statements about nitrogen fixation is correct?

Accepted Answer

It is the process by which nitrogen gas (N$$_2) is $$converted to ammonia (NH$$_4^+) by $$certain bacteria.

Question 8

Which of the following best describes a facultative anaerobe?

Accepted Answer

An organism that can grow with or without oxygen, using aerobic respiration, anaerobic respiration, or fermentation.

Question 9

Which of the following is a real-world example of a biofilm?

Accepted Answer

Dental plaque on teeth.

Question 10

Why is water essential for microbial growth?

Accepted Answer

Water dissolves enzymes, salts, and nutrients required for metabolism.

Question 11

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

Cell division rate equals cell death rate; population size remains constant.

Question 12

Which of the following is a trace element required in small amounts for microbial growth?

Accepted Answer

Iron (Fe)

Question 13

Which of the following is a growth factor for bacteria?

Accepted Answer

Vitamins that cannot be synthesized by the organism

Question 14

Which of the following best explains why obligate anaerobes cannot survive in the presence of oxygen?

Accepted Answer

They lack enzymes such as catalase to detoxify reactive oxygen species.

Question 15

Which of the following is a correct statement about the effect of temperature on microbial membranes?

Accepted Answer

At low temperatures, membranes become rigid and fragile; at high temperatures, they become too fluid.

Question 16

Which of the following is a correct pairing of organism and its energy and carbon source?

Accepted Answer

Photoautotroph: light for energy, CO$$_2$$ for carbon

Question 17

Which of the following best describes the process of quorum sensing in biofilm formation?

Accepted Answer

It is the process by which bacteria communicate and coordinate gene expression based on cell density.

Question 18

Which of the following is a reason why bacterial endospores can survive for millions of years?

Accepted Answer

They are metabolically inactive and resistant to desiccation.

Question 19

Which of the following best describes an obligate halophile?

Accepted Answer

An organism that requires high salt concentrations for growth.

Question 20

Which of the following methods is used to estimate microbial population size by diluting a sample and counting colonies?

Accepted Answer

Serial dilution and standard plate count

Microbial Nutrition and Growth: Study Guide for Chapter 6

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