Question 1

Which of the following best describes the function of superoxide dismutase (SOD) in aerobic microorganisms?

Accepted Answer

It converts superoxide radicals into oxygen and hydrogen peroxide, reducing oxidative stress.

Question 2

A bacterium isolated from a deep-sea hydrothermal vent is found to grow optimally at 90°C and can survive at temperatures up to 113°C. Which term best describes this organism?

Accepted Answer

Hyperthermophile

Question 3

Which of the following statements about MacConkey agar is TRUE?

Accepted Answer

It is both selective and differential, inhibiting Gram-positives and differentiating lactose fermenters.

Question 4

A patient is infected with a bacterium that is a Gram-negative, non-spore forming, motile curved rod, and causes severe wound infections and sepsis. Based on these features, which organism is most likely responsible?

Accepted Answer

Vibrio vulnificus

Question 5

Which of the following best explains why penicillin is only effective against actively growing bacteria?

Accepted Answer

Penicillin inhibits the cross-linking of peptidoglycan, which only occurs during cell wall synthesis in dividing cells.

Question 6

A microbiologist wants to count only the living bacteria in a sample. Which method should they use, and what is the result typically expressed as?

Accepted Answer

Viable plate count; colony forming units (CFUs)

Question 7

Which of the following best describes the role of siderophores in bacterial physiology?

Accepted Answer

They are small molecules that scavenge iron from the environment for uptake into the cell.

Question 8

A continuous culture device that maintains a constant cell density by automatically adjusting the flow rate of fresh medium based on turbidity measurements is called a:

Accepted Answer

Turbidostat

Question 9

Which of the following equations correctly calculates the generation time ($$G) $$for a bacterial culture, given total time ($$t) $$and number of generations ($$n$$)?

Accepted Answer

$$G = \frac{t}{n}$$

Question 10

A bacterium is found to be an obligate anaerobe. Which of the following statements is most accurate regarding its growth and oxygen tolerance?

Accepted Answer

It is killed by exposure to oxygen and cannot grow in its presence.

Question 11

Which of the following best describes the function of the MreB protein in bacteria?

Accepted Answer

It determines rod shape and directs peptidoglycan synthesis.

Question 12

A microbiologist is working with a heat-sensitive vitamin solution that must be sterilized. Which physical control method is most appropriate?

Accepted Answer

Filtration through a 0.22 $$\mum $$membrane filter

Question 13

Which of the following is a correct statement about the bacterial cell wall and the action of lysozyme?

Accepted Answer

Lysozyme hydrolyzes the $$\beta-1$$,4-glycosidic bonds between NAG and NAM.

Question 14

Which of the following best explains why smaller bacterial cells generally grow and divide faster than larger ones?

Accepted Answer

They have a higher surface area-to-volume ratio, facilitating faster nutrient uptake and waste removal.

Question 15

Which of the following best describes the main ecological role of methanogenic archaea in the environment?

Accepted Answer

They produce methane as a byproduct of anaerobic metabolism, contributing to global methane emissions.

Question 16

A researcher is using a semi-log plot to analyze bacterial growth. What is the main advantage of plotting cell numbers logarithmically?

Accepted Answer

It converts the exponential growth phase into a straight line, simplifying calculation of growth rates.

Question 17

Which of the following best describes the difference between selective and differential media?

Accepted Answer

Selective media favors the growth of specific microbes while inhibiting others, whereas differential media distinguishes between groups based on biological characteristics.

Question 18

Which of the following is a correct calculation for colony forming units (CFU) if 50 colonies are counted on a plate from a 1:10,000 dilution and 0.1 mL was plated?

Accepted Answer

$$	ext{CFU} = \frac{50}{0.1} 	imes 10,000$$

Question 19

Which of the following best describes the function of the Sec system in bacteria?

Accepted Answer

It translocates unfolded proteins across the plasma membrane using ATP hydrolysis.

Question 20

A patient is diagnosed with a urinary tract infection caused by Enterococcus faecalis. Which of the following characteristics is LEAST likely to be associated with this organism?

Accepted Answer

Spore formation

Microbial Growth, Nutrition, and Bacterial Cell Structure: Study Guide for Exam #2

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