Question 1

Which of the following best describes a biofilm?

Accepted Answer

A community of microorganisms protected by a polysaccharide and protein matrix.

Question 2

During which stage of biofilm development do cells detach to colonize new surfaces?

Accepted Answer

Dispersal

Question 3

Quorum sensing in bacteria is best described as:

Accepted Answer

A process by which bacteria detect their own population density using extracellular signaling molecules.

Question 4

In a closed system, which phase of microbial growth is characterized by equal rates of cell division and cell death?

Accepted Answer

Stationary phase

Question 5

Which equation best represents the conversion of superoxide to hydrogen peroxide by superoxide dismutase?

Accepted Answer

$$2\ \mathrm{O_2$^-} + 2\ \mathrm{H^+} \rightarrow \mathrm{H_2O_2} + \mathrm{O_2$}$$

Question 6

A bacterium that thrives in the human stomach is most likely a(n):

Accepted Answer

Acidophile

Question 7

Which class of microbes would you expect to find in a hot spring with temperatures around 70°C?

Accepted Answer

Thermophiles

Question 8

What is the main advantage of using chemically defined media in microbial experiments?

Accepted Answer

The exact composition of the media is known and can be controlled.

Question 9

Which of the following best describes a chemoorganoheterotroph?

Accepted Answer

Uses organic molecules as both an energy and carbon source.

Question 10

Which plating method is most appropriate for isolating a single bacterial species from a mixed culture?

Accepted Answer

Streak-plate method

Question 11

A scientist wants to measure the turbidity of a bacterial culture to estimate its biomass. Which instrument should she use?

Accepted Answer

Spectrophotometer

Question 12

Which of the following statements about halophiles is correct?

Accepted Answer

They require moderate concentrations of salt (1-14%) to survive.

Question 13

Which type of media would you use to differentiate between alpha-hemolytic and beta-hemolytic bacteria?

Accepted Answer

Differential media

Question 14

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

Accepted Answer

Converts hydrogen peroxide to water and oxygen.

Question 15

Which environmental classification would best fit Methanopyrus kandleri, an archaeal species living in hydrothermal vents at 100-122°C and not requiring oxygen?

Accepted Answer

Hyperthermophile & Obligate Anaerobe

Question 16

Which of the following is NOT a type of culture media?

Accepted Answer

Descriptive media

Question 17

What must be assumed when using the plate counting method for measuring microbial growth?

Accepted Answer

Each colony counted on a plate is formed from a single cell.

Question 18

Which of the following best describes an obligate aerobe?

Accepted Answer

Requires oxygen for metabolism.

Question 19

Which of the following is a characteristic of viable cells in a plate count assay?

Accepted Answer

All of the above.

Question 20

Which of the following best describes a photoautotroph?

Accepted Answer

Obtains energy from sunlight and carbon from CO$$_2.$$

Microbial Growth: Environmental and Nutritional Factors, Cultivation, and Measurement

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