Question 1

Which phase of the microbial growth curve is characterized by a balance between cell division and cell death, resulting in no net increase in cell number?

Accepted Answer

Stationary phase

Question 2

A microbiologist is culturing bacteria in a closed system. After several hours, the number of viable cells begins to decrease. Which phase of the growth curve is being observed?

Accepted Answer

Death phase

Question 3

Which of the following best describes a defined medium?

Accepted Answer

Exact chemical composition is known

Question 4

A patient develops a joint infection after receiving an artificial hip implant. Which microbial growth form is most likely responsible for the persistent infection?

Accepted Answer

Sessile cells in a biofilm

Question 5

Which of the following equations represents the reduction of molecular oxygen to water?

Accepted Answer

$$O_2 + 4e^- + 4H$$^+ \rightarrow 2H_2O$$

Question 6

Which class of microorganisms would most likely thrive in an environment with a pH of 2?

Accepted Answer

Acidophiles

Question 7

A bacterium that can grow in 15% NaCl but not in 25% NaCl is best classified as which of the following?

Accepted Answer

Halophile

Question 8

Which of the following statements about bacteriostatic agents is correct?

Accepted Answer

They inhibit important biochemical processes and bind weakly

Question 9

A disk diffusion assay is used to test the effectiveness of an antibiotic. What does a large zone of inhibition around a disk indicate?

Accepted Answer

The antibiotic is effective at inhibiting the test organism

Question 10

Which of the following best describes the mechanism of action of quinolones?

Accepted Answer

Interfere with DNA gyrase and prevent DNA supercoiling

Question 11

A patient is prescribed a broad-spectrum antibiotic. What does this mean?

Accepted Answer

The antibiotic is effective against both Gram-positive and Gram-negative bacteria

Question 12

Which of the following drugs inhibits the synthesis of mycolic acid and is effective only against Mycobacterium?

Accepted Answer

Isoniazid

Question 13

Why are antifungal drugs more likely to have toxic side effects in humans compared to antibacterial drugs?

Accepted Answer

Fungi are eukaryotic and share many cellular features with humans

Question 14

Which of the following is a correct statement about the minimum inhibitory concentration (MIC)?

Accepted Answer

It is the smallest amount of an agent needed to inhibit growth of a microorganism

Question 15

A new antibiotic is found to inhibit fatty acid synthesis in bacteria. Which of the following best describes its likely spectrum of activity?

Accepted Answer

Broad-spectrum, effective against MRSA and vancomycin-resistant enterococci

Question 16

Which of the following is a major reason for using drug combination therapy in the treatment of HIV infections?

Accepted Answer

To reduce the probability of the virus developing resistance

Question 17

Which of the following best explains why molecular oxygen ($$O_2) is $$toxic to some microorganisms?

Accepted Answer

Oxygen is converted to toxic byproducts such as superoxide anion and hydrogen peroxide

Question 18

Which of the following is a property of a selective medium?

Accepted Answer

It contains compounds that inhibit the growth of some microbes but not others

Question 19

A patient is treated with a drug that binds to the 30S subunit of the bacterial ribosome. Which class of antibiotics is most likely being used?

Accepted Answer

Aminoglycosides

Question 20

Which of the following best describes the action of an antiseptic?

Accepted Answer

Used to reduce microbial numbers on living tissues

Microbial Growth and Its Control – Study Notes

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