Question 1

Which of the following best describes a chemoautotroph?

Accepted Answer

An organism that uses inorganic chemicals as an energy source and carbon dioxide as a carbon source.

Question 2

Which enzyme is responsible for converting superoxide anion ($$O_2$$^{-}$$) into hydrogen peroxide (H_2O_2$) in aerobic organisms?

Accepted Answer

Superoxide dismutase

Question 3

A bacterium is found growing only at the bottom of a fluid thioglycollate medium tube. Which of the following best describes its oxygen requirement?

Accepted Answer

Obligate anaerobe

Question 4

Which of the following toxic forms of oxygen is the most reactive and has the shortest half-life in cells?

Accepted Answer

Hydroxyl radical ($$OH\cdot)$$

Question 5

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

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species.

Question 6

A microbe isolated from a hot spring in Yellowstone National Park grows optimally at 90°C. Which category does it belong to?

Accepted Answer

Hyperthermophile

Question 7

Which of the following equations correctly represents the reaction catalyzed by catalase?

Accepted Answer

$$2 H_2O_2 \rightarrow 2 H_2O + O_2$

Question 8

Which of the following best describes a facultative anaerobe?

Accepted Answer

It can grow with or without oxygen, but grows better with oxygen.

Question 9

Which of the following is a real-world example of a barophile?

Accepted Answer

A bacterium isolated from deep-sea hydrothermal vents.

Question 10

Which of the following statements about osmotic pressure and microbial growth is correct?

Accepted Answer

Facultative halophiles can tolerate high salt concentrations but do not require them.

Question 11

A bacterium that grows best at pH 3 is classified as a:

Accepted Answer

Acidophile

Question 12

Which of the following is a growth factor for bacteria?

Accepted Answer

NADH

Question 13

Which of the following best explains why most bacteria cannot grow in honey?

Accepted Answer

Honey has a low water activity, which inhibits microbial growth.

Question 14

Which of the following is NOT a correct pairing of organism and its growth environment?

Accepted Answer

Vibrio fischeri – alkalinophile

Question 15

Which of the following is a correct description of nitrogen fixation?

Accepted Answer

The reduction of nitrogen gas ($$N_2) to $$ammonia ($$NH_3) by $$certain prokaryotes.

Question 16

Which of the following best describes the effect of high temperature on the lipid-containing membranes of cells?

Accepted Answer

Membranes become too fluid and may not contain the cell.

Question 17

Which of the following is a multi-step process involving both superoxide dismutase and catalase?

Accepted Answer

$$4 O_2$^{-} + 4 H^+ \rightarrow 2 H_2O + 3 O_2$

Question 18

Which of the following best describes the growth pattern of microaerophiles in fluid thioglycollate medium?

Accepted Answer

Growth just below the surface where oxygen concentration is low.

Question 19

Which of the following is a real-life application of understanding osmotic pressure in microbiology?

Accepted Answer

Using salt to preserve meats by creating a hypertonic environment.

Question 20

Which of the following best explains why endospores can survive for years in dry environments?

Accepted Answer

They cease most metabolic activity and retain water within their structure.

Microbial Nutrition and Growth: Study Notes

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