Question 1

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

Accepted Answer

A single cell elongates, replicates its DNA, forms a cross-wall, and separates into two identical cells.

Question 2

A bacterial culture starts with 10 cells. If the generation time is 20 minutes, how many cells will there be after 2 hours, assuming exponential growth? Use the formula $$N_f = (N_i)2^n.$$

Accepted Answer

$$N_f = 10 	imes 2^6$ = 640$$

Question 3

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

Accepted Answer

Stationary phase

Question 4

Which method would be most appropriate for counting only live bacterial cells in a water sample?

Accepted Answer

Viable count using the plate count method

Question 5

A bacterium that grows optimally at 37°C and is commonly found in the human body is classified as a:

Accepted Answer

Mesophile

Question 6

Which of the following equations correctly represents the action of catalase in detoxifying hydrogen peroxide?

Accepted Answer

$$2 \mathrm{H}_2\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{O}_2$$

Question 7

Which type of microorganism would you expect to find growing in a jar of pickles with a pH of 3?

Accepted Answer

Acidophile

Question 8

A bacterium that can survive and grow in the presence of high salt concentrations is called a:

Accepted Answer

Facultative halophile

Question 9

Which of the following best describes an obligate anaerobe?

Accepted Answer

Cannot grow in the presence of oxygen

Question 10

Why is the 'danger zone' (between 20°C and 50°C) important in food safety?

Accepted Answer

Bacteria grow rapidly and may produce toxins in this temperature range.

Question 11

Which of the following is a trace element required by bacteria for enzyme function?

Accepted Answer

Zinc

Question 12

A scientist wants to culture a microaerophile. Which of the following setups would be most appropriate?

Accepted Answer

Candle jar

Question 13

Which of the following best explains why a cell placed in a hypertonic solution shrinks?

Accepted Answer

Water leaves the cell, causing plasmolysis.

Question 14

Which of the following best describes a fastidious bacterium?

Accepted Answer

It requires many organic growth factors from the environment.

Question 15

A bacterial culture is measured using a spectrophotometer. What does an increase in turbidity indicate?

Accepted Answer

An increase in the number of bacterial cells

Question 16

Which of the following is NOT a method for measuring bacterial growth?

Accepted Answer

Gram staining

Question 17

Which of the following best describes a facultative anaerobe?

Accepted Answer

Can grow with or without oxygen, but grows better with oxygen

Question 18

Which of the following is a correct description of a chemotroph?

Accepted Answer

Uses chemical compounds as an energy source

Question 19

Nitrogen-fixing bacteria are important in the environment because they:

Accepted Answer

Convert atmospheric nitrogen (N2) into a usable form for plants

Question 20

Which of the following best explains why deep rice containers cool more slowly and are more prone to Bacillus cereus growth than shallow containers?

Accepted Answer

Heat is retained longer in deeper containers, keeping the temperature in the danger zone for longer.

Microbial Growth: Nutrition, Environmental Factors, and Measurement

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