Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses organic compounds as both an energy and carbon source.

Question 2

A bacterium is found growing at the bottom of the ocean near hydrothermal vents, where temperatures exceed 100$$^	ext{o}C $$and pressure is extremely high. Which terms best describe this organism?

Accepted Answer

Hyperthermophile and barophile

Question 3

Which equation correctly calculates the number of bacteria present after $$n$$ generations, starting with $$b$$ bacteria?

Accepted Answer

$$B = b 	imes 2^n$$

Question 4

A culture starts with 5 cells and has a generation time of 30 minutes. How many cells will there be after 3 hours?

Accepted Answer

320

Question 5

Which enzyme is responsible for converting superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) and oxygen (O_2$)?

Accepted Answer

Superoxide dismutase

Question 6

Why are obligate anaerobes unable to survive in the presence of oxygen?

Accepted Answer

They lack the enzymes needed to detoxify reactive oxygen species.

Question 7

Which of the following best explains why salt is used to preserve food?

Accepted Answer

Salt creates a hypertonic environment, causing water to leave microbial cells and inhibiting growth.

Question 8

Which of the following is a direct method for counting microbial cells that does NOT require incubation?

Accepted Answer

Coulter counter

Question 9

A bacterial culture is growing in a chemostat. What is the main advantage of using a chemostat for microbial growth?

Accepted Answer

It allows for the continuous removal of waste and addition of fresh medium, maintaining the culture in a specific growth phase.

Question 10

Which of the following best describes the role of nitrogen-fixing bacteria in the nitrogen cycle?

Accepted Answer

They convert atmospheric nitrogen ($$N_2) to $$ammonia ($$NH_3).$$

Question 11

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms involve complex synergistic relationships and often use quorum sensing to coordinate behavior.

Question 12

A bacterium is classified as a facultative anaerobe. Which of the following best describes its growth in the presence and absence of oxygen?

Accepted Answer

It grows better in the presence of oxygen but can survive without it.

Question 13

Which of the following growth factors is required for the synthesis of folic acid and nucleic acids?

Accepted Answer

Para-aminobenzoic acid (PABA)

Question 14

A culture medium contains a high concentration of salt. Which type of microorganism is most likely to thrive in this environment?

Accepted Answer

Obligate halophile

Question 15

Which of the following best explains why most human pathogens are classified as mesophiles?

Accepted Answer

They grow best at temperatures between 20$$^	ext{o}C $$and 40$$^	ext{o}C$$, which includes human body temperature.

Question 16

Which of the following is an example of an indirect method for estimating microbial population size?

Accepted Answer

Turbidity measurement using a spectrophotometer

Question 17

A scientist wants to estimate the number of bacteria in a water sample that does not grow well on solid media. Which method should they use?

Accepted Answer

Most probable number (MPN)

Question 18

Which of the following statements about generation time is correct?

Accepted Answer

Generation time is the time required for a bacterial cell to grow and divide.

Question 19

Which of the following best describes the effect of temperature on microbial membranes?

Accepted Answer

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

Question 20

Which of the following equations is used to calculate generation time ($$G) $$given a time interval ($$t) $$and number of generations ($$n$$)?

Accepted Answer

$$G = t / n$$

Microbial Nutrition, Growth, and Population Dynamics

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