Q: A bacterial culture is grown for 3 hours and produces 6 generations. What is the generation time ($$g) in $$minutes?

$$g = \frac{3 \text{ hours} \times 60 \text{ min/hour}}{6} = 30 \text{ min}$$

Question 1

Which of the following statements best explains why viruses are considered exceptions to the classic definition of a microorganism?

Accepted Answer

Viruses are not living because they lack key characteristics of life.

Question 2

Which of the following is a unique feature of archaeal cell membranes compared to bacterial cell membranes?

Accepted Answer

Use of ether linkages and terpenoid lipids for increased stability.

Question 3

A microbiologist isolates a bacterium that can survive in extremely high salt concentrations (20% NaCl). Which adaptation is most likely present in this organism?

Accepted Answer

Specialized pumps to export Na+ and import K+.

Question 4

Which of the following best describes the function of the FtsZ protein in bacterial cell division?

Accepted Answer

It forms a ring at the center of the cell to direct septum formation.

Question 5

A bacterium is found to grow optimally at 4°C and has highly flexible membrane lipids. Which classification best fits this organism?

Accepted Answer

Psychrophile

Question 6

Which of the following is a reason why peptidoglycan synthesis is a common target for antibiotics?

Accepted Answer

Peptidoglycan is essential for bacterial cell wall integrity and not present in humans.

Question 7

Which of the following best describes a biofilm?

Accepted Answer

A surface-attached, collaborative community of microorganisms embedded in an extracellular matrix.

Question 8

A bacterial culture is grown for 3 hours and produces 6 generations. What is the generation time ($$g) in $$minutes?

Accepted Answer

$$g = \frac{3 	ext{ hours} 	imes 60 	ext{ min/hour}}{6} = 30 	ext{ min}$$

Question 9

Which of the following is NOT a function of the bacterial capsule?

Accepted Answer

Acts as a crystalline protein S-layer for motility.

Question 10

Which of the following statements about Koch’s postulates is correct?

Accepted Answer

They require the disease-causing organism to be isolated and grown in pure culture.

Question 11

Which of the following best describes the difference between facilitated diffusion and active transport in bacteria?

Accepted Answer

Active transport requires energy input, while facilitated diffusion does not.

Question 12

A bacterium is found to grow only in the absence of oxygen and lacks enzymes such as catalase and superoxide dismutase. How would you classify this organism?

Accepted Answer

Obligate anaerobe

Question 13

Which of the following media would you use to select for Gram-negative bacteria and differentiate lactose fermenters?

Accepted Answer

MacConkey agar

Question 14

Which of the following adaptations would you expect to find in a thermophilic bacterium?

Accepted Answer

Stable proteins with hydrogen bonds and saturated fatty acids in the membrane.

Question 15

Which of the following is a correct formula for calculating the final number of cells ($$N) in a $$bacterial culture, given the initial number ($$N_0) $$and the number of generations ($$n$$)?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 16

Which of the following physical agents is NOT effective at killing bacterial endospores?

Accepted Answer

Boiling water

Question 17

A microbiologist is studying a bacterium that forms a specialized cell for nitrogen fixation, surrounded by three extra cell walls and a specialized envelope. What is this structure called?

Accepted Answer

Heterocyst

Question 18

Which of the following best describes the function of siderophores in bacteria?

Accepted Answer

They are secreted to scavenge iron from the environment.

Question 19

Which of the following is a plausible reason why 99% of microorganisms are considered unculturable in the laboratory?

Accepted Answer

They require specific growth factors not provided in standard media.

Question 20

Which of the following best explains why the discovery of antibiotics in the early 1900s led to a decline in the use of phage therapy?

Accepted Answer

Antibiotics were easier to mass-produce and use than phages.

Microbiology: Foundations, Cell Structure, Growth, and Environmental Adaptations

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