Question 1

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

Accepted Answer

A cell elongates, forms a septum, and divides into two genetically identical daughter cells.

Question 2

During which phase of the bacterial growth curve does the population size remain constant due to nutrient depletion or waste accumulation?

Accepted Answer

Stationary phase

Question 3

A culture of Escherichia coli starts with 100 cells. If the generation time is 20 minutes, how many cells will there be after 1 hour?

Accepted Answer

1600

Question 4

Which equation correctly relates the initial and final cell numbers during exponential growth?

Accepted Answer

$$N = N_0$ 2^n$$

Question 5

In a chemostat, which parameter is primarily used to control the growth rate of the microbial culture?

Accepted Answer

Dilution rate ($$F/V)$$

Question 6

What happens to a bacterial population in a chemostat if the dilution rate is set too high?

Accepted Answer

The population washes out and cell density drops to zero.

Question 7

Which temperature class of microorganisms would most likely be found in deep-sea hydrothermal vents?

Accepted Answer

Hyperthermophiles

Question 8

A bacterium that grows optimally at pH 3.5 is classified as a(n):

Accepted Answer

Acidophile

Question 9

Helicobacter pylori is able to survive in the acidic environment of the stomach primarily because it:

Accepted Answer

Uses urease to convert urea to ammonia, neutralizing stomach acid

Question 10

Which of the following best explains why moist heat is more effective than dry heat for sterilization?

Accepted Answer

Moist heat penetrates cells and denatures proteins more efficiently.

Question 11

Which of the following is NOT a toxic byproduct of oxygen metabolism in cells?

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 12

A facultative anaerobe grows better in the presence of oxygen because:

Accepted Answer

Aerobic respiration yields more ATP than anaerobic respiration or fermentation.

Question 13

Which of the following best describes the effect of water activity ($$a_w) on $$microbial growth?

Accepted Answer

Microbial growth is limited as $$a_w$$ decreases due to less available water.

Question 14

Which physical method of microbial control is most appropriate for sterilizing heat-sensitive liquids?

Accepted Answer

Filtration

Question 15

Ultraviolet (UV) radiation kills microorganisms primarily by:

Accepted Answer

Inducing thymine dimers in DNA, disrupting replication

Question 16

Which of the following statements about the autoclave is correct?

Accepted Answer

The high temperature achieved by steam under pressure is responsible for sterilization.

Question 17

A researcher wants to maintain a bacterial culture in exponential phase for several weeks. Which system should they use?

Accepted Answer

Continuous culture (chemostat)

Question 18

If a bacterial culture is exposed to a hypertonic environment, what is the most likely outcome?

Accepted Answer

Water will leave the cell, causing plasmolysis.

Question 19

Which of the following best explains why endospores are more resistant to ionizing radiation than vegetative cells?

Accepted Answer

Endospores contain protective proteins and DNA repair enzymes.

Question 20

A liquid sample is to be sterilized by membrane filtration. Which pore size would be most effective for removing all bacteria, including the smallest known bacterial cells?

Accepted Answer

0.1 μm

Microbial Growth and Its Control: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards