Question 1

Which of the following best describes the difference between a microbe's tolerance for an environmental condition and its optimal condition for growth?

Accepted Answer

Tolerance refers to the range in which a microbe can survive, while optimal condition is where it grows fastest.

Question 2

A bacterium that grows best at 37°C but can survive at 25°C is classified as which of the following?

Accepted Answer

Mesophile

Question 3

Which of the following is NOT a macronutrient required for microbial growth?

Accepted Answer

Zinc (Zn)

Question 4

A bacterium is found growing in a hot spring at 85°C. Which term best describes its temperature preference?

Accepted Answer

Hyperthermophile

Question 5

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

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

Question 6

A microbiologist wants to culture a fastidious bacterium that requires many growth factors. Which type of medium should she use?

Accepted Answer

Complex medium

Question 7

Which of the following equations correctly represents the calculation for the number of cells after $$n$$ generations, starting with $$N_0$$ cells?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 8

A bacterium is inoculated into a fluid thioglycollate medium and grows only at the bottom of the tube. What is the most likely oxygen requirement of this organism?

Accepted Answer

Obligate anaerobe

Question 9

Which of the following best describes a selective medium?

Accepted Answer

A medium that inhibits the growth of some microbes while allowing others to grow.

Question 10

A bacterial culture is in the stationary phase of growth. Which of the following best describes what is happening?

Accepted Answer

The rate of cell division equals the rate of cell death.

Question 11

Which of the following is a function of superoxide dismutase (SOD) in bacteria?

Accepted Answer

It neutralizes superoxide radicals ($$O_2$$^-$$) produced during aerobic metabolism.

Question 12

A bacterium that can grow in the presence or absence of oxygen, but does not use oxygen for metabolism, is best described as:

Accepted Answer

Aerotolerant anaerobe

Question 13

Which of the following best describes a differential medium?

Accepted Answer

A medium that allows visualization of metabolic differences between organisms.

Question 14

A culture starts with 10 cells and doubles every 30 minutes. How many cells will there be after 3 hours?

Accepted Answer

640

Question 15

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

Accepted Answer

Staphylococcus aureus growing on an indwelling catheter

Question 16

Which of the following best explains why buffers are added to microbial growth media?

Accepted Answer

To maintain a stable pH and prevent inhibition of microbial growth due to acid production.

Question 17

Which of the following is a chemical requirement for microbial growth that is often supplied as a growth factor in media for fastidious organisms?

Accepted Answer

Vitamins

Question 18

A bacterium that thrives in a high-salt environment, such as 10% NaCl, is best described as:

Accepted Answer

Halophilic

Question 19

Which of the following best describes the lag phase in a batch culture growth curve?

Accepted Answer

Cells are acclimating to the environment and not dividing rapidly.

Question 20

Which of the following statements about defined and complex media is correct?

Accepted Answer

Defined media have a precisely known chemical composition, while complex media contain ingredients of unknown composition.

Microbial Growth: Physical and Chemical Requirements, Media, and Growth Dynamics

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