Question 1

Which of the following best explains why obligate anaerobes cannot survive in the presence of oxygen?

Accepted Answer

They lack the enzymes superoxide dismutase and catalase to detoxify reactive oxygen species (ROS).

Question 2

A clinical sample is streaked onto eosin methylene blue (EMB) agar. After incubation, pink colonies are observed. What can you conclude about the bacteria?

Accepted Answer

They are Gram-negative and ferment lactose.

Question 3

Which of the following equations correctly represents the action of catalase in detoxifying hydrogen peroxide?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 4

A microbiologist wants to grow a fastidious organism that requires several amino acids and vitamins. Which type of media should be used?

Accepted Answer

Complex media

Question 5

Which of the following best describes a facultative anaerobe?

Accepted Answer

It can grow with or without oxygen, switching between aerobic respiration and fermentation.

Question 6

A water treatment plant needs to ensure that all endospores are destroyed in a batch of water. Which method should be used?

Accepted Answer

Autoclaving at $$121^\circ C$$ and 15 psi for at least 15 minutes

Question 7

Which of the following statements about macronutrients and micronutrients is correct?

Accepted Answer

Macronutrients are needed in large amounts, such as carbon, while micronutrients are needed in trace amounts, such as iron.

Question 8

A patient sample is collected for microbiological analysis. Which of the following is the most important reason for using aseptic technique during collection?

Accepted Answer

To prevent contamination of the sample with external microbes

Question 9

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

Accepted Answer

Selective media inhibit the growth of some microbes while allowing others to grow; differential media distinguish between microbes based on metabolic traits.

Question 10

Which of the following best explains why Mycobacterium species are difficult to control with standard disinfectants?

Accepted Answer

They have cell walls rich in mycolic acids, making them resistant to many chemicals.

Question 11

A microbiologist is testing the effectiveness of a new disinfectant. She finds that it kills 90% of bacteria every 5 minutes. What is the decimal reduction time ($$D$$ value) for this disinfectant?

Accepted Answer

$$5$$ minutes

Question 12

Which of the following best describes the process of nitrogen fixation?

Accepted Answer

Conversion of atmospheric $$N_2$$ into organic nitrogen compounds by certain microbes

Question 13

Which of the following is a real-world application of HEPA filtration?

Accepted Answer

Removing airborne microbes and allergens from hospital air

Question 14

A laboratory is using a chemically defined medium to grow a microbe. Which of the following is true about this medium?

Accepted Answer

All chemical components and their exact concentrations are known.

Question 15

Which of the following best describes the action of superoxide dismutase?

Accepted Answer

It converts superoxide ions ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$).

Question 16

A food manufacturer wants to count the number of viable bacteria in a yogurt sample. Which method should be used?

Accepted Answer

Viable plate count using spread or pour plate method

Question 17

Which of the following statements about autoclaving is correct?

Accepted Answer

It uses pressurized steam to achieve sterilization, killing all microbes including endospores.

Question 18

Which of the following best explains why UV radiation is not suitable for sterilizing large volumes of liquid?

Accepted Answer

UV light has poor penetrating power and cannot reach microbes deep within the liquid.

Question 19

A hospital is deciding how to decontaminate equipment that contacts mucous membranes but does not penetrate tissues. Which level of germicide is required?

Accepted Answer

High-level or intermediate-level germicide to ensure removal of bacteria, fungi, and viruses, with low numbers of endospores

Question 20

Which of the following best describes a fastidious organism?

Accepted Answer

It requires multiple growth factors and will not grow if they are missing from the environment.

Chap 7B

Study Guide - Practice Questions

Study Guide - Flashcards