Question 1

Which of the following best describes the function of a chemostat in microbial culture?

Accepted Answer

It allows for the continuous addition of fresh medium and removal of spent medium, maintaining steady-state growth.

Question 2

A microbiologist is culturing a marine bacterium that requires NaCl for growth. Which term best describes this organism?

Accepted Answer

Halophile

Question 3

Which of the following equations correctly expresses the relationship between the initial number of cells ($$N_0$$), the number of generations ($$n$$), and the final number of cells ($$N_t) in a $$batch culture?

Accepted Answer

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

Question 4

A sample of E. coli is grown in a batch culture. The initial cell count is $$5 	imes 10^7$ and after 2 hours the count is 1$$ 	imes $$10^8. $$What is the generation time ($$g) in $$hours?

Accepted Answer

$$g = 2$$ hours

Question 5

Which of the following best explains why the viable plate count method may underestimate the total number of cells in a natural sample?

Accepted Answer

Many organisms have different nutrient and growth requirements that are not met by the culture medium.

Question 6

Which of the following is a key adaptation of psychrophilic enzymes that allows them to function at low temperatures?

Accepted Answer

More α-helices and fewer β-sheets, resulting in greater flexibility

Question 7

A bacterial culture is measured for turbidity at 540 nm using a spectrophotometer. What is the unit of measurement for this method?

Accepted Answer

Optical density (OD)

Question 8

Which of the following best describes the function of superoxide dismutase in aerobic microorganisms?

Accepted Answer

It converts superoxide anion ($$O_2$$^-$$) to hydrogen peroxide (H_2O_2$) and oxygen (O_2$).

Question 9

Which of the following best explains why EMB agar is considered both selective and differential?

Accepted Answer

It contains dyes that inhibit Gram-positive bacteria and differentiates lactose fermenters by color change.

Question 10

Which of the following statements about biofilms is correct?

Accepted Answer

Biofilms provide a protective environment that can increase resistance to harmful chemicals.

Question 11

A microbiologist wants to culture an obligate anaerobe. Which of the following techniques would be most appropriate?

Accepted Answer

Use a reducing agent such as thioglycolate in the medium and incubate in an anoxic jar.

Question 12

Which of the following best describes the role of compatible solutes in halophilic microorganisms?

Accepted Answer

They help maintain positive water balance by accumulating in the cytoplasm without inhibiting cellular processes.

Question 13

Which of the following is a correct statement about the cardinal temperatures of microbial growth?

Accepted Answer

The optimum temperature is typically closer to the maximum than to the minimum.

Question 14

A culture medium contains peptone, beef extract, and agar, but the exact chemical composition is unknown. This medium is best described as:

Accepted Answer

Complex medium

Question 15

Which of the following best explains why batch cultures eventually enter the stationary phase?

Accepted Answer

Nutrient depletion and waste accumulation limit further growth.

Question 16

Which of the following is a correct formula for calculating the specific growth rate ($$k) of a $$microbial population?

Accepted Answer

$$k = 0.693 / g$$

Question 17

A microbiologist is using a Petroff–Hausser counting chamber to estimate cell numbers. Which of the following is a limitation of this method?

Accepted Answer

It cannot distinguish between live and dead cells unless a special stain is used.

Question 18

Which of the following best describes the growth of Streptomyces under nutrient-limited conditions?

Accepted Answer

Multiple fission resulting in the formation of many spores from a single filamentous cell.

Question 19

Which of the following statements about acidophiles is correct?

Accepted Answer

Their cytoplasmic membranes require protons for stability and may lyse at neutral pH.

Microbial Nutrition, Growth, and Environmental Influences: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards