Question 1

Which of the following best describes the definition of microbial growth?

Accepted Answer

An increase in the number of cells

Question 2

A clinical specimen is collected from a patient and must be transported to the laboratory. Which of the following is the most important reason for using transport media?

Accepted Answer

To prevent the death of the suspected pathogen

Question 3

Which of the following equations correctly calculates the number of cells in a bacterial population after n generations, starting with $$N_0$$ cells?

Accepted Answer

$$N_t = N_0$ 	imes 2^n$$

Question 4

A bacterium is isolated from a hot spring and grows optimally at 75°C. Which category does this organism belong to?

Accepted Answer

Thermophile

Question 5

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

Accepted Answer

They lack superoxide dismutase and catalase to detoxify reactive oxygen species

Question 6

A microbiologist wants to isolate a pure culture from a mixed clinical specimen. Which technique should be used for qualitative isolation?

Accepted Answer

Quadrant streaking

Question 7

Which of the following media would be most appropriate for isolating Staphylococcus aureus from a skin swab?

Accepted Answer

Mannitol salt agar (MSA)

Question 8

A urine sample is serially diluted and plated using the pour plate method. After incubation, 150 colonies are counted on a plate inoculated with 0.1 mL of a $$10^{-4}$$ dilution. What is the original concentration of bacteria in the urine sample (CFU/mL)?

Accepted Answer

$$1.5 	imes 10^7$

Question 9

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are composed of a single bacterial species

Question 10

Which of the following best describes a facultative anaerobe?

Accepted Answer

Grows best with oxygen but can grow without it

Question 11

A patient is suspected of having a Streptococcus infection. Which laboratory test would help differentiate Streptococcus from Staphylococcus?

Accepted Answer

Catalase test

Question 12

Which of the following is a selective and differential medium for Gram-negative bacilli that ferment lactose?

Accepted Answer

Eosin methylene blue (EMB) agar

Question 13

Which of the following is a trace element required for the function of certain bacterial enzymes?

Accepted Answer

Zinc

Question 14

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

Accepted Answer

Alkalinophile

Question 15

Which of the following is NOT a requirement for successfully culturing a clinical specimen?

Accepted Answer

Presence of antibiotics in the medium

Question 16

Which of the following best describes the function of catalase in bacteria?

Accepted Answer

Converts hydrogen peroxide to water and oxygen

Question 17

A microbiologist is using a spectrophotometer to estimate bacterial growth. What is being measured in this method?

Accepted Answer

Turbidity (cloudiness) of the culture

Question 18

Which of the following best describes a fastidious bacterium?

Accepted Answer

Requires special growth factors and nutrients

Question 19

Which of the following is a direct method for measuring microbial growth that distinguishes between live and dead cells?

Accepted Answer

Viable plate count

Question 20

Which of the following statements about generation time is TRUE?

Accepted Answer

It is the time required for a bacterial cell to divide into two cells

Microbial Nutrition and Growth: Core Concepts and Laboratory Applications

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