Question 1

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

A bacterial cell replicates its DNA, elongates, forms a cross wall, and splits into two genetically identical daughter cells.

Question 2

Which type of culture medium would you use to distinguish between two closely related bacterial species based on their ability to ferment lactose?

Accepted Answer

Differential medium

Question 3

A microbiologist wants to isolate a pure culture from a mixed bacterial sample. Which method is most appropriate for this purpose?

Accepted Answer

Streak plate technique

Question 4

Which of the following equations correctly models exponential bacterial growth?

Accepted Answer

$$N_t = N_0$ e$$^{r t}$$

Question 5

During which phase of the bacterial growth curve is the generation time shortest and population growth rate highest?

Accepted Answer

Exponential (log) phase

Question 6

A water sample is suspected to contain a low concentration of bacteria. Which direct method would be most effective for quantifying viable bacteria in this sample?

Accepted Answer

Membrane filtration followed by colony counting

Question 7

Which of the following statements about selective media is correct?

Accepted Answer

Selective media contain substances that inhibit the growth of some microbes while allowing others to grow.

Question 8

A microbiologist needs to preserve a bacterial culture for decades without significant loss of viability. Which method should be used?

Accepted Answer

Lyophilization (freeze-drying)

Question 9

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

Cell division rate equals cell death rate; population size remains constant.

Question 10

A researcher uses a spectrophotometer to measure the optical density (OD$$_{600}) of a $$bacterial culture. What is this method primarily measuring?

Accepted Answer

The total cell density based on light scattering (turbidity)

Question 11

Which of the following is a key advantage of the pour-plate method over the streak-plate method?

Accepted Answer

It allows for the quantification of viable cells and is suitable for anaerobic or microaerophilic species.

Question 12

Which of the following best describes the difference between arithmetic and logarithmic (exponential) growth in bacteria?

Accepted Answer

Arithmetic growth adds a constant number of cells per unit time, while exponential growth doubles the population each generation.

Question 13

Which culture medium would be most appropriate for transporting a clinical specimen to the laboratory without significant microbial growth?

Accepted Answer

Transport medium

Question 14

A microbiologist is testing for the presence of Enterobacteriaceae in a food sample. Which medium would allow both selection for Gram-negative bacteria and differentiation based on lactose fermentation?

Accepted Answer

MacConkey agar

Question 15

Which of the following is a limitation of using turbidity (optical density) to estimate bacterial population size?

Accepted Answer

It cannot distinguish between live and dead cells.

Question 16

Given the logistic growth equation $$\frac{dN}{dt} = r_{max} N \left(1 - \frac{N}{K}\right)$$, what does the term $$K$$ represent?

Accepted Answer

The carrying capacity of the environment

Question 17

Which direct method would be most appropriate for counting both live and dead bacterial cells in a milk sample?

Accepted Answer

Microscopic count using a Petroff-Hausser chamber

Question 18

A clinical laboratory receives a specimen suspected of containing fastidious bacteria. Which type of medium should be used to maximize the chances of recovery?

Accepted Answer

Complex medium

Question 19

Which of the following best explains why the streak-plate method requires sterilization of the loop between each quadrant?

Accepted Answer

To dilute the number of cells and achieve isolated colonies

Question 20

A researcher is comparing two bacterial cultures: one growing in a closed flask and one in a chemostat with continuous nutrient supply. Which growth phase is likely to be prolonged in the chemostat compared to the closed system?

Accepted Answer

Exponential (log) phase

Microbial Nutrition and Growth II: Culture Methods, Media, and Bacterial Growth

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