Question 1

Which of the following best describes the difference between defined and complex media used in laboratory culture of microorganisms?

Accepted Answer

Defined media have a precise chemical composition known, while complex media are composed of digests of chemically undefined substances.

Question 2

A bacterium is found to require only trace amounts of zinc for growth. Zinc in this context is best classified as:

Accepted Answer

A micronutrient

Question 3

Which macromolecule makes up the largest percentage of dry weight in an E. coli cell?

Accepted Answer

Protein

Question 4

Which of the following statements about autotrophs and heterotrophs is correct?

Accepted Answer

Autotrophs use carbon dioxide ($$CO_2) as $$their carbon source, while heterotrophs use organic carbon sources.

Question 5

Which of the following is a function of magnesium (Mg) in microbial cells?

Accepted Answer

Stabilizes ribosomes, membranes, and nucleic acids

Question 6

A researcher is culturing a nutritionally demanding microorganism. Which type of media should they use to ensure optimal growth?

Accepted Answer

Enriched media

Question 7

Which of the following best explains why iron (Fe) is considered a micronutrient for most microorganisms?

Accepted Answer

It is a key component of cytochromes and FeS proteins involved in electron transport.

Question 8

Which of the following is NOT a typical application of differential media in microbiology?

Accepted Answer

To selectively inhibit the growth of some microbes but not others

Question 9

Which element is most abundant by dry weight in a typical bacterial cell?

Accepted Answer

Carbon (C)

Question 10

A scientist observes isolated masses of cells on a solid medium after incubation. What are these masses called?

Accepted Answer

Colonies

Question 11

Which of the following is a plausible consequence of using gelatin instead of agar as a gelling agent in solid media?

Accepted Answer

Gelatin melts at lower temperatures, potentially liquefying the medium during incubation.

Question 12

Which of the following best describes a pure culture?

Accepted Answer

A culture containing only a single kind of microbe

Question 13

Which of the following is a common misconception about macronutrients and micronutrients in microbial nutrition?

Accepted Answer

Micronutrients are never essential for microbial growth.

Question 14

Which of the following statements about growth factors is correct?

Accepted Answer

Growth factors are organic compounds required in small amounts by certain organisms.

Question 15

Which of the following is most likely to be found in an enriched medium?

Accepted Answer

Additional nutrients to support the growth of nutritionally demanding organisms

Question 16

Which of the following is a plausible reason why sodium (Na) is required by some microbes?

Accepted Answer

It is required for marine microbes to maintain osmotic balance.

Question 17

Which of the following is a correct statement about the use of selective media?

Accepted Answer

Selective media contain compounds that inhibit the growth of some microbes but not others.

Question 18

Which of the following elements is a key component of sulfur-containing amino acids and some vitamins?

Accepted Answer

Sulfur (S)

Question 19

Which of the following is a plausible effect of omitting phosphorus from a defined medium?

Accepted Answer

Cells would be unable to synthesize nucleic acids and phospholipids.

Question 20

Which of the following is a plausible explanation for why calcium (Ca) is important in some microbes?

Accepted Answer

It stabilizes cell walls and is required for the heat stability of endospores.

Microbial Metabolism: Nutritional Requirements, Laboratory Culture, and Energy Pathways

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