Question 1

Which of the following best describes a facultative anaerobe?

Accepted Answer

Can grow with or without oxygen, but grows best with oxygen present.

Question 2

A bacterium that grows optimally at 15°C and can survive at 0°C is classified as a:

Accepted Answer

Psychrophile

Question 3

Which of the following equations correctly represents the number of cells after n generations, starting from a single cell?

Accepted Answer

$$N = 2^n$$

Question 4

A culture medium that contains yeast extract and peptone, but whose exact chemical composition is unknown, is best described as:

Accepted Answer

Complex medium

Question 5

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are more susceptible to microbicides than planktonic cells.

Question 6

Which enzyme is responsible for converting hydrogen peroxide into water and oxygen in bacteria?

Accepted Answer

Catalase

Question 7

A bacterium that can tolerate high salt concentrations, such as Staphylococcus on human skin, is classified as a:

Accepted Answer

Facultative halophile

Question 8

Which of the following best explains why food in a deep container cools more slowly and is more prone to spoilage than food in a shallow container?

Accepted Answer

The surface area to volume ratio is lower, so heat escapes more slowly.

Question 9

Which of the following is NOT a chemical requirement for microbial growth?

Accepted Answer

Osmotic pressure

Question 10

A laboratory is working with a highly infectious airborne pathogen. Which biosafety level (BSL) is required?

Accepted Answer

BSL-3

Question 11

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

Accepted Answer

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

Question 12

Which of the following methods would be most appropriate for counting bacteria in a water sample with very low bacterial concentration?

Accepted Answer

Filtration followed by plate count

Question 13

Which of the following statements about agar is TRUE?

Accepted Answer

Agar is a complex polysaccharide used as a solidifying agent in culture media.

Question 14

A medium that contains 7% NaCl and a pH indicator to distinguish mannitol fermenters is best described as:

Accepted Answer

Both selective and differential

Question 15

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

Accepted Answer

Removes superoxide radicals by converting them to oxygen and hydrogen peroxide.

Question 16

A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours?

Accepted Answer

$$N = 2$$^{6}$$ = 64$$

Question 17

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

Accepted Answer

To minimize pH changes caused by microbial metabolism.

Question 18

Which of the following is a real-world example of a selective medium?

Accepted Answer

Sabouraud’s dextrose agar for isolating fungi

Question 19

Which of the following is NOT a direct method for measuring microbial growth?

Accepted Answer

Turbidity measurement

Question 20

A patient develops an infection on a heart valve after surgery. Which microbial property is most likely responsible for the persistence of this infection?

Accepted Answer

The bacteria form biofilms on the heart valve.

Microbial Growth: Physical and Chemical Requirements, Culture Methods, and Measurement

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