Question 1

Which of the following best describes the main difference between arithmetic and logarithmic growth in bacterial populations?

Accepted Answer

Logarithmic growth results in a rapid increase in cell number, while arithmetic growth is slow and steady.

Question 2

A clinical specimen must be collected and delivered to the laboratory promptly. Which of the following is the primary responsibility for ensuring this?

Accepted Answer

The patient's physician

Question 3

Which type of culture medium would you use to selectively grow fungi from a soil sample containing both bacteria and fungi?

Accepted Answer

Selective medium with a slightly acidic pH

Question 4

During which phase of the microbial growth curve are bacteria most susceptible to antimicrobial agents?

Accepted Answer

Log (exponential) phase

Question 5

Which of the following best describes a facultative anaerobe?

Accepted Answer

Can grow with or without oxygen but prefers oxygen.

Question 6

Which enzyme is responsible for converting superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) in aerobic bacteria?

Accepted Answer

Superoxide dismutase (SOD)

Question 7

Nitrogen fixation is essential for life on Earth because:

Accepted Answer

It converts nitrogen gas ($$N_2) $$into ammonia ($$NH_3$$), which can be used by living organisms.

Question 8

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

Accepted Answer

Ultraviolet light

Question 9

A bacterium that grows best at pH 3.0 is classified as a(n):

Accepted Answer

Acidophile

Question 10

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are more susceptible to antibiotics than planktonic cells.

Question 11

Quorum sensing in bacteria is best described as:

Accepted Answer

A process by which bacteria sense and respond to population density using signaling molecules.

Question 12

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

Accepted Answer

They lack the enzymes needed to detoxify toxic forms of oxygen.

Question 13

A bacterium isolated from a hot spring that grows optimally at 90°C is classified as a(n):

Accepted Answer

Extreme thermophile (hyperthermophile)

Question 14

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

Accepted Answer

Dental plaque on teeth

Question 15

Which of the following best describes the role of exopolysaccharides in biofilm formation?

Accepted Answer

They form a protective matrix that holds the biofilm together.

Question 16

Which of the following best describes an obligate halophile?

Accepted Answer

An organism that requires high salt concentrations (up to 30%) for growth.

Question 17

Which of the following is a multi-step process that bacteria use to regulate gene expression during biofilm development?

Accepted Answer

Quorum sensing

Question 18

A bacterium that can survive in the presence of oxygen but does not use it for metabolism is called a(n):

Accepted Answer

Aerotolerant anaerobe

Question 19

Which of the following is a correct equation for the detoxification of hydrogen peroxide by catalase?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 20

Which of the following would be the best strategy to prevent biofilm formation on medical devices, based on the study materials?

Accepted Answer

Blocking homoserine lactone signaling molecules with furanones

Microbial Nutrition, Growth, and Biofilms: Study Notes for MIC 205

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