Question 1

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

A process where a parent cell divides into two genetically identical daughter cells after chromosome replication and septum formation

Question 2

A microbiologist wants to maintain a bacterial culture in the log phase for optimal production of a pharmaceutical compound. Which system should be used?

Accepted Answer

Chemostat with continuous addition of fresh medium and removal of waste

Question 3

A bacterial culture is grown for 2 hours and goes through 6 generations. What is the generation time? Use the formula $$	ext{Generation time} = \frac{	ext{Growth time (minutes)}}{	ext{Number of generations}}.$$

Accepted Answer

$$\frac{120}{6} = 20$$ minutes

Question 4

Which phase of the bacterial growth curve is characterized by a balance between cell division and cell death due to nutrient depletion and waste accumulation?

Accepted Answer

Stationary phase

Question 5

Which of the following best explains why biofilms are a major concern in healthcare settings?

Accepted Answer

Biofilms are difficult to treat and contribute to persistent infections on indwelling devices

Question 6

A bacterium isolated from a hot spring grows optimally at 70°C. Which classification best describes this organism?

Accepted Answer

Thermophile

Question 7

Which of the following statements about halophiles is correct?

Accepted Answer

Halophiles thrive in high-salt environments by maintaining high concentrations of organic materials and ions in their cytoplasm

Question 8

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

Accepted Answer

Superoxide dismutase

Question 9

A microbe that grows throughout a thioglycolate broth, but with denser growth at the top, is most likely a(n):

Accepted Answer

Facultative anaerobe

Question 10

Which of the following best describes a fastidious microbe?

Accepted Answer

A microbe that requires multiple growth factors supplied in the medium

Question 11

Which type of media would you use to visually distinguish between beta-hemolytic and alpha-hemolytic bacteria?

Accepted Answer

Differential media

Question 12

A clinical sample is suspected to contain both Gram-positive and Gram-negative bacteria. Which medium would best allow for isolation and differentiation of these organisms?

Accepted Answer

Eosin methylene blue (EMB) agar

Question 13

Which of the following is a direct method for counting microbial cells?

Accepted Answer

Viable plate count

Question 14

Which physical method is most effective for ensuring the elimination of bacterial endospores from laboratory glassware?

Accepted Answer

Autoclaving at 121°C and 15 psi for 20 minutes

Question 15

A disinfectant is tested and found to kill 90% of a bacterial population in 5 minutes at a set temperature. What is the decimal reduction time (D value) for this disinfectant?

Accepted Answer

$$D = 5$$ minutes

Question 16

Which chemical agent is classified as a high-level germicide and is effective against endospores at high concentrations?

Accepted Answer

Hydrogen peroxide

Question 17

A patient develops an infection after a piercing at a kiosk. The antiseptic used was half-empty and opened a month earlier. What is the most likely role of the antiseptic in pathogen transmission?

Accepted Answer

It may have become contaminated and served as a reservoir for pathogens

Question 18

Which of the following best describes the action of ionizing radiation in microbial control?

Accepted Answer

It generates reactive ions that damage nucleic acids and can penetrate packaging

Question 19

Which of the following is a reason why prions are difficult to eliminate from surgical instruments?

Accepted Answer

They are resistant to both chemical sterilization and autoclaving

CH. 7 Fundamentals of Microbial Growth and Decontamination

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