Question 1

Which of the following is NOT a basic requirement for microbial life?

Accepted Answer

Sunlight

Question 2

A bacterium is found in an environment with extremely low phosphorus (P) availability. Which evolutionary adaptation would most likely provide the greatest benefit?

Accepted Answer

Reduce genome size

Question 3

Which of the following best describes a trace element in microbial nutrition?

Accepted Answer

An inorganic micronutrient typically found as a cofactor in enzymes

Question 4

Which of the following statements about defined media is correct?

Accepted Answer

Its precise chemical composition is known

Question 5

A medium contains only the following: 1 g/L glucose, 0.2 g/L NH4Cl, 0.2 g/L Na2HPO4, 0.1 g/L MgSO4, 0.1 g/L KCl, trace elements, vitamins, and 50 mg/L ampicillin. What type of medium is this?

Accepted Answer

Defined and selective

Question 6

Which type of culture medium would you use to isolate bacteria that are resistant to bile salts?

Accepted Answer

Bile salts agar

Question 7

MacConkey agar is an example of which type of medium?

Accepted Answer

Selective and differential

Question 8

Which method would be most appropriate for enriching rare nitrogen-fixing bacteria from soil?

Accepted Answer

Use a medium lacking any nitrogen source except atmospheric N$$_2$$

Question 9

What is the main purpose of the streak plate technique in microbiology?

Accepted Answer

To obtain isolated colonies from a mixed culture

Question 10

Which of the following is a limitation of direct microscopic cell counts?

Accepted Answer

They are laborious and prone to human error

Question 11

A milk sample is serially diluted and plated. At the 10$$^{-6}$$ dilution, you count 250 colonies from 1 mL plated. What is the bacterial concentration in the original sample (in cells/mL)?

Accepted Answer

$$2.5 	imes 10^8$

Question 12

Why do direct microscopic counts of natural samples often yield much higher cell numbers than viable plate counts?

Accepted Answer

Many cells in natural samples are not culturable under laboratory conditions

Question 13

Which of the following best describes the principle of spectrophotometric measurement of microbial growth?

Accepted Answer

It measures light scattering by cells, reported as optical density

Question 14

Why is it necessary to create a standard curve when using spectrophotometry to estimate cell numbers?

Accepted Answer

Because cell shape and size affect light scattering

Question 15

Which of the following is a growth factor required by some bacteria?

Accepted Answer

Amino acids

Question 16

A researcher wants to isolate a pure culture of a single bacterial strain from a mixed sample. Which method should they use?

Accepted Answer

Direct isolation using streak or spread plate

Question 17

Which of the following is a correct assumption when performing viable plate counts?

Accepted Answer

Each colony arises from a single cell

Question 18

Which wavelength of light provides higher sensitivity for spectrophotometric measurement of microbial growth?

Accepted Answer

$$450\ \mathrm{nm}$$

Question 19

Which of the following best describes the function of vitamins in microbial nutrition?

Accepted Answer

They often function as coenzymes in enzymatic reactions

Microbial Nutrition, Cultivation, and Measurement of Growth

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