Question 1

Which of the following best describes the primary difference between autotrophs and heterotrophs in terms of carbon acquisition?

Accepted Answer

Autotrophs obtain carbon from CO$$_2$$ and fix it into organic molecules, while heterotrophs obtain carbon from preformed organic compounds.

Question 2

A bacterium is found to grow only at the top of a thioglycolate broth tube. Which of the following best describes its oxygen requirements?

Accepted Answer

It is an obligate aerobe.

Question 3

Which pathway is primarily used by photosynthetic green sulfur bacteria for CO$$_2$$ fixation?

Accepted Answer

Reverse citric acid cycle

Question 4

What is the main function of siderophores in bacteria such as Escherichia coli?

Accepted Answer

To bind and transport iron into the cell

Question 5

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

Accepted Answer

Superoxide dismutase

Question 6

Nitrogenase, the enzyme complex responsible for nitrogen fixation, is highly sensitive to which environmental factor?

Accepted Answer

Oxygen

Question 7

Which of the following is a macronutrient required in large amounts by bacterial cells?

Accepted Answer

Magnesium (Mg)

Question 8

A marine bacterium uses Na$$^+-$$powered ATP synthase. What is the likely role of sodium in this organism?

Accepted Answer

It stabilizes cell walls and powers ATP synthesis.

Question 9

Which of the following best explains why heterocysts are important for nitrogen fixation in some cyanobacteria?

Accepted Answer

They sequester nitrogen fixation away from oxygen, protecting nitrogenase.

Question 10

Which of the following is a trace element required by some microorganisms for specific enzyme function?

Accepted Answer

Manganese (Mn)

Question 11

A bacterium is able to grow throughout a thioglycolate broth tube but grows best at the top. What is its oxygen relationship?

Accepted Answer

Facultative aerobe

Question 12

Which of the following reactions is catalyzed by catalase?

Accepted Answer

$$2 H_2O_2 \rightarrow 2 H_2O + O_2$

Question 13

Which macromolecule makes up the largest percentage of dry weight in a typical bacterial cell?

Accepted Answer

Protein

Question 14

Which of the following is a real-world application of bacterial siderophores?

Accepted Answer

They are used by bacteria to initiate infection by sequestering iron from animal tissues.

Question 15

Which of the following best describes the role of calcium in bacterial endospores?

Accepted Answer

It forms a complex with dipicolinic acid to stabilize the endospore.

Question 16

Which of the following is a toxic form of oxygen that can damage cellular components?

Accepted Answer

Hydroxyl radical ($$OH^\cdot)$$

Question 17

Which of the following is a growth factor that may be required by some microorganisms?

Accepted Answer

Amino acids

Question 18

A laboratory is attempting to culture an obligate anaerobe. Which of the following methods would be most appropriate?

Accepted Answer

Use an anoxic jar with a palladium catalyst.

Question 19

Which of the following best explains why iron is typically needed in larger amounts than other trace metals in microorganisms?

Accepted Answer

Iron is required for electron transport chain proteins.

Question 20

Which of the following is a correct net reaction for the hydroxypropionate pathway?

Accepted Answer

$$2 CO_2$ + 4 H + 2 ATP \rightarrow C_3H_4O_3 + H_2O$$

Microbial Nutrition and Metabolism: Essential Elements, Pathways, and Growth Factors

Study Guide - Practice Questions