Question 1

Which of the following best describes a chemoorganoheterotroph?

Accepted Answer

Uses organic molecules for energy, electrons, and carbon.

Question 2

A bacterium isolated from the Great Salt Lake requires 25% NaCl for growth. What is the best classification for this organism?

Accepted Answer

Obligate halophile

Question 3

Which enzyme is responsible for converting superoxide radicals (O$$_2$$^{\bullet-}$$) into hydrogen peroxide (H_2$O_2$) and oxygen (O_2$)?

2$$\,$$O_2$$^{\bullet-} + 2\,H^+ \xrightarrow{SOD} $$O_2 + H_2O_2$

Accepted Answer

Superoxide dismutase (SOD)

Question 4

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

Accepted Answer

They lack the enzymes needed to detoxify reactive oxygen species.

Question 5

A microbe that grows best at pH 2.5 and is isolated from the Tinto River is most likely a(n):

Accepted Answer

Acidophile

Question 6

Which process in the nitrogen cycle is carried out by Rhizobium and some cyanobacteria?

$$N_2$$ \rightarrow $$NH_3$$

Accepted Answer

Nitrogen fixation

Question 7

A bacterium that can grow in the presence or absence of oxygen, but grows better with oxygen, is classified as a:

Accepted Answer

Facultative anaerobe

Question 8

Which of the following is a real-life example of a biofilm causing disease?

Accepted Answer

Dental plaque leading to tooth decay

Question 9

Which of the following best describes the role of quorum sensing in biofilms?

Accepted Answer

It enables bacteria to communicate and coordinate gene expression based on population density.

Question 10

A bacterium isolated from a hydrothermal vent at 90$$^\circC is $$most likely a:

Accepted Answer

Hyperthermophile

Question 11

Which of the following is a correct sequence for the microbial growth curve?

Accepted Answer

Lag phase → Log (exponential) phase → Stationary phase → Death (decline) phase

Question 12

Which of the following is a trace element required by some enzymes as a cofactor?

Accepted Answer

Iron (Fe)

Question 13

A bacterium that grows only at the top of a thioglycollate broth tube is most likely a(n):

Accepted Answer

Obligate aerobe

Question 14

Which of the following best explains why Mycobacterium tuberculosis can survive for months in dry conditions?

Accepted Answer

Its cell wall retains water.

Question 15

Which of the following is a correct equation for the catalase reaction?

$$2\,H_2O_2 \xrightarrow{catalase} 2\,H_2O + O_2$

Accepted Answer

Catalase converts hydrogen peroxide to water and oxygen.

Question 16

Which of the following organisms is most likely to be found growing in refrigerated foods and can cause disease?

Accepted Answer

Listeria monocytogenes

Question 17

Which of the following is a real-life consequence of biofilm formation in healthcare settings?

Accepted Answer

Increased risk of infection from catheters and implanted devices

Question 18

Which of the following best describes the effect of high temperature on microbial cells?

Accepted Answer

It denatures proteins and makes membranes too fluid.

Question 19

Which of the following is a function of sulfur in microbial nutrition?

Accepted Answer

Component of sulfur-containing amino acids and vitamins

Question 20

A bacterium that grows best in water at pH 9.0 is classified as a(n):

Accepted Answer

Alkalinophile

Microbial Nutrition and Growth: Essential Requirements and Environmental Factors

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