Question 1

Which of the following best describes microbial growth?

Accepted Answer

An increase in the number of cells

Question 2

A bacterium isolated from a hot spring in Yellowstone Park grows optimally at 70°C. Which group does it most likely belong to?

Accepted Answer

Thermophiles

Question 3

Which of the following statements about acidophiles is correct?

Accepted Answer

They grow optimally at pH values below 4

Question 4

Why is honey effective at preserving food from microbial spoilage?

Accepted Answer

It has a high osmotic pressure that causes plasmolysis in microbes

Question 5

Which of the following is a chemical requirement for microbial growth that is required for the synthesis of proteins but NOT nucleic acids?

Accepted Answer

Sulfur

Question 6

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

Accepted Answer

Facultative anaerobe

Question 7

Which enzyme is responsible for neutralizing superoxide free radicals ($$O_2$$^-$$) in bacteria?

Accepted Answer

Superoxide dismutase (SOD)

Question 8

Which of the following best describes a selective medium?

Accepted Answer

It suppresses the growth of unwanted bacteria and encourages the growth of desired bacteria

Question 9

A microbiologist wants to isolate a pure culture from a mixed sample. Which method should they use?

Accepted Answer

Streak plate method

Question 10

Which biosafety level (BSL) requires the use of sealed, negative pressure labs and full-body, air-supplied suits?

Accepted Answer

BSL-4

Question 11

A scientist is measuring the cloudiness of a bacterial culture using a spectrophotometer. Which method of measuring microbial growth are they using?

Accepted Answer

Turbidity

Question 12

Which of the following is a disadvantage of the plate count method for measuring bacterial populations?

Accepted Answer

It requires serial dilutions to obtain countable plates

Question 13

Which type of culture medium is described as having an exact chemical composition that is known?

Accepted Answer

Chemically defined medium

Question 14

A microbiologist is working with a bacterium that cannot synthesize its own vitamins. What are these vitamins called?

Accepted Answer

Organic growth factors

Question 15

Which of the following best explains why high salt or sugar concentrations are used to preserve foods?

Accepted Answer

They cause plasmolysis in microbial cells, inhibiting growth

Question 16

Which phase of the bacterial growth curve is characterized by a period of intense metabolic activity but no increase in cell number?

Accepted Answer

Lag phase

Question 17

A sample contains a very small number of bacteria. Which direct measurement method would be most appropriate to quantify them?

Accepted Answer

Filtration

Question 18

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are always composed of a single bacterial species

Question 19

Which of the following equations correctly represents the exponential growth of bacteria by binary fission, where $$N is $$the final number of cells, $$N_0 is $$the initial number of cells, and $$n is $$the number of generations?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 20

Which of the following is NOT a direct method for measuring microbial growth?

Accepted Answer

Turbidity

Microbial Growth: Physical and Chemical Requirements, Culture Methods, and Measurement

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