Question 1

Which of the following best describes an obligate aerobe?

Accepted Answer

A microorganism that requires oxygen for growth and cannot survive without it

Question 2

A facultative anaerobe is best defined as an organism that:

Accepted Answer

Can grow with or without oxygen, but grows better with oxygen

Question 3

Which of the following equations correctly represents aerobic respiration?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP}$$

Question 4

Which of the following is NOT a characteristic of fermentation?

Accepted Answer

It produces more ATP than aerobic respiration

Question 5

A microbe that grows only at the bottom of a thioglycollate broth tube is most likely:

Accepted Answer

An obligate anaerobe

Question 6

Which of the following best describes the lag phase of bacterial growth?

Accepted Answer

Cells are adjusting to their environment and not dividing rapidly

Question 7

Which type of medium would you use to isolate a bacterium that can ferment lactose from a mixed culture?

Accepted Answer

MacConkey agar

Question 8

Which of the following statements about selective media is correct?

Accepted Answer

Selective media contain substances that inhibit the growth of some organisms while allowing others to grow

Question 9

Which of the following is a differential medium?

Accepted Answer

MacConkey agar

Question 10

A patient sample is streaked on Mannitol Salt Agar (MSA). Yellow colonies appear. What does this indicate?

Accepted Answer

The organism is likely Staphylococcus aureus, which ferments mannitol

Question 11

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase

Question 12

Which phase of the bacterial growth curve is characterized by the equation $$N_t = N_0$ 	imes 2^n$$?

Accepted Answer

Log (exponential) phase

Question 13

Which of the following is true about the stationary phase of bacterial growth?

Accepted Answer

The number of new cells equals the number of dying cells

Question 14

Which of the following best describes a complex medium?

Accepted Answer

A medium containing extracts from yeast, meat, or plants

Question 15

Which of the following is a reason why bacteria enter the death phase?

Accepted Answer

Accumulation of toxic waste products

Question 16

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

Accepted Answer

Breaks down hydrogen peroxide into water and oxygen

Question 17

A bacterium that grows best in high salt concentrations is called:

Accepted Answer

Halophile

Question 18

Which of the following is the best example of a selective and differential medium?

Accepted Answer

MacConkey agar

Question 19

Which of the following is a real-life application of using differential media in a clinical laboratory?

Accepted Answer

Identifying lactose fermenters among Enterobacteriaceae in a stool sample

Question 20

Which of the following best describes the purpose of using a streak plate method in microbiology?

Accepted Answer

To isolate pure colonies from a mixed culture

Microbiology Study Guide: Oxygen Requirements, Growth, and Media Types

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