Question 1

Which of the following best describes the main advantage of biofilm formation for bacteria in a clinical setting?

Accepted Answer

Biofilms protect bacteria from antibiotics and immune responses.

Question 2

A chemostat is used to maintain a continuous culture of bacteria. Which parameter directly controls the growth rate of the population?

Accepted Answer

Dilution rate (rate at which fresh medium is added)

Question 3

Which equation correctly relates the number of generations ($$n) to $$the initial ($$N_0) $$and final ($$N) $$cell numbers in exponential growth?

Accepted Answer

$$n = \frac{\log N - \log N_0$}{\log 2}$$

Question 4

A batch culture of E. coli is grown in a closed system. After several hours, the cell density plateaus. What is the most likely explanation?

Accepted Answer

An essential nutrient has been depleted or waste products have accumulated.

Question 5

Which of the following is a limitation of using microscopic counts to estimate microbial cell numbers?

Accepted Answer

It cannot distinguish between live and dead cells without special stains.

Question 6

If a bacterial culture starts with $$N_0 = 100$ cells and reaches N = 800$ cells, how many generations (n$) have occurred? Use n$$ = \$$log_2$$($$N/N_0$$)$$.

Accepted Answer

$$n = 3$$

Question 7

Which phase of the microbial growth curve is characterized by a balance between cell division and cell death?

Accepted Answer

Stationary phase

Question 8

Which of the following best explains why exponential growth cannot continue indefinitely in a natural environment?

Accepted Answer

Resource limitation and waste accumulation eventually slow growth.

Question 9

Which of the following is a macronutrient required in large amounts by bacteria?

Accepted Answer

Phosphorus (P)

Question 10

A disinfectant claims to kill 99.9% of germs on contact. If you start with $$1 	imes 10^6$ cells, how many remain after treatment?

Accepted Answer

$$1 	imes 10^3$

Question 11

Which of the following best describes the difference between planktonic and sessile bacterial growth?

Accepted Answer

Sessile growth involves attachment to surfaces and can lead to biofilm formation.

Question 12

Which of the following statements about chemostats is TRUE?

Accepted Answer

Chemostats can maintain exponential growth for extended periods.

Question 13

Which process is directly inhibited by penicillins during bacterial cell division?

Accepted Answer

Transpeptidation in peptidoglycan synthesis

Question 14

A culture is grown in a chemostat with a limiting nutrient. What happens if the dilution rate is set too high?

Accepted Answer

The cells will be washed out of the vessel.

Question 15

Which of the following is a key difference between exponential and logistic growth?

Accepted Answer

Logistic growth includes a plateau phase due to resource limitation.

Question 16

Which of the following best describes the lag phase in a batch culture growth curve?

Accepted Answer

Cells are adapting to new conditions and preparing for division.

Question 17

Which of the following is a limitation of using turbidimetric (optical density) measurements to estimate cell numbers?

Accepted Answer

It cannot distinguish between live and dead cells.

Question 18

Which of the following is an example of a micronutrient required by bacteria?

Accepted Answer

Iron (Fe)

Question 19

Which of the following best explains why motile cells must be immobilized for accurate microscopic counting?

Accepted Answer

Motile cells can move out of the field of view, leading to inaccurate counts.

Question 20

A culture starts with $$1 	imes 10^2$ cells and grows to 1$$ 	imes $$10^5$$ cells. Using $$n = 3.3 	imes (\log_{10} N - \log_{10} N_0$)$$, how many generations have occurred?

Accepted Answer

$$n = 9.9$$

Microbial Growth: Cell Division, Population Dynamics, and Measurement

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