Q: A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours of log-phase growth? Use the formula $$N = N_0$ \times 2^n$$, where $$n is $$the number of generations.

$$N = 1 \times 2$$^{12}$$ = 4096$$

Question 1

A microbiologist is studying bacteria isolated from a deep-sea hydrothermal vent where temperatures regularly exceed 90°C. Which group would these bacteria most likely belong to?

Accepted Answer

Hyperthermophiles

Question 2

Why are buffers commonly added to bacterial culture media?

Accepted Answer

To minimize changes in pH during microbial growth

Question 3

A patient receives an intravenous solution with a high salt concentration. What is the most likely effect on bacteria contaminating the IV line?

Accepted Answer

Bacterial cells will undergo plasmolysis due to water loss

Question 4

Which element is primarily required for the synthesis of nucleic acids and cell membranes in bacteria?

Accepted Answer

Phosphorus

Question 5

A culture of bacteria is found to grow equally well in the presence or absence of oxygen, but uses fermentation when oxygen is not available. How should these bacteria be classified?

Accepted Answer

Facultative anaerobes

Question 6

Which enzyme is responsible for breaking down hydrogen peroxide into water and oxygen in aerobic bacteria?

Accepted Answer

Catalase

Question 7

A hospital patient develops a catheter-associated infection. The bacteria are found to be embedded in a slimy matrix and are resistant to antibiotics. What microbial structure is most likely responsible?

Accepted Answer

Biofilm

Question 8

Which of the following best describes a pure culture?

Accepted Answer

A culture containing only one species or strain of microbe

Question 9

A laboratory wants to preserve a bacterial strain for several years. Which method involves freezing the cells and then dehydrating them in a vacuum?

Accepted Answer

Lyophilization

Question 10

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

Accepted Answer

Stationary phase

Question 11

A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours of log-phase growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2$$^{12}$$ = 4096$$

Question 12

Which direct method of measuring bacterial growth involves counting colonies on plates after serial dilution?

Accepted Answer

Plate count

Question 13

A scientist uses a spectrophotometer to measure the cloudiness of a bacterial culture. Which method of measuring cell growth is being used?

Accepted Answer

Turbidity

Question 14

Which of the following is a trace element required by bacteria as an enzyme cofactor?

Accepted Answer

Iron

Question 15

A bacterium is found to require oxygen but only grows when the oxygen concentration is lower than that of the atmosphere. How is this bacterium classified?

Accepted Answer

Microaerophile

Question 16

Which of the following best explains why high salt concentrations inhibit the growth of most bacteria?

Accepted Answer

Salt causes water to leave the cell, leading to plasmolysis

Question 17

Which of the following is NOT a function of sulfur in microbial cells?

Accepted Answer

Structural backbone of organic molecules

Question 18

A researcher is isolating a pure culture from a mixed sample. Which technique is most appropriate for obtaining isolated colonies?

Accepted Answer

Streak plate method

Question 19

Which toxic form of oxygen is neutralized by the enzyme superoxide dismutase (SOD)?

Accepted Answer

Superoxide radicals

Question 20

A food microbiologist is investigating spoilage in refrigerated foods. Which group of bacteria is most likely responsible for growth at these low temperatures?

Accepted Answer

Psychrotrophs

Chapter 6

Study Guide - Practice Questions

Study Guide - Flashcards