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, exponential increase in cell number, while arithmetic growth increases cell number by a constant amount each generation.

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 equations correctly represents the action of superoxide dismutase (SOD) in detoxifying reactive oxygen species?

Accepted Answer

$$2O_2^- + 2H^+ \xrightarrow{SOD} H_2O_2 + O_2$

Question 6

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

Accepted Answer

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

Question 7

Nitrogen fixation is essential for life on Earth because:

Accepted Answer

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

Question 8

Which of the following best describes a facultative anaerobe?

Accepted Answer

An organism that can grow with or without oxygen but prefers oxygen.

Question 9

A bacterium isolated from a hot spring grows optimally at 70°C. How would you classify this organism?

Accepted Answer

Thermophile

Question 10

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are more susceptible to antibiotics than planktonic cells.

Question 11

Which process allows bacteria in a biofilm to coordinate gene expression based on population density?

Accepted Answer

Quorum sensing

Question 12

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

Accepted Answer

Dental plaque on teeth

Question 13

Which of the following best describes the role of furanones produced by red algae in biofilm prevention?

Accepted Answer

They block homoserine lactone signaling molecules, disrupting quorum sensing.

Question 14

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

Accepted Answer

Ultraviolet light

Question 15

A bacterium that grows best at pH 9.5 is classified as a(n):

Accepted Answer

Alkalinophile

Question 16

Which of the following best explains why most cells die in the absence of water?

Accepted Answer

Water is required to dissolve enzymes and nutrients for metabolism.

Question 17

Which of the following equations represents the breakdown of hydrogen peroxide by catalase?

Accepted Answer

$$2H_2O_2 \xrightarrow{catalase} 2H_2O + O_2$

Question 18

Which of the following best describes an obligate halophile?

Accepted Answer

An organism that grows in high salt concentrations, up to 30%.

Question 19

Which of the following is a correct combination of energy and carbon source for a photoautotroph?

Accepted Answer

Light for energy, $$CO_2$$ for carbon

Question 20

Which of the following is a reason why biofilm-associated bacteria are more resistant to antibiotics than planktonic bacteria?

Accepted Answer

Biofilms act as molecular filters, reducing drug activity and penetration.

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

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