Question 1

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

Accepted Answer

A process where a single cell divides into two identical daughter cells after DNA replication and septum formation.

Question 2

A bacterial culture starts with 10 cells. If the generation time is 30 minutes, how many cells will there be after 3 hours? Use the formula $$N_f = (N_i)2^n.$$

Accepted Answer

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

A microbiologist wants to estimate the number of viable bacteria in a water sample. Which method should they use?

Accepted Answer

Viable count using the plate count method

Question 5

Which of the following best explains why psychrotrophs can cause food spoilage in refrigerated foods?

Accepted Answer

They can grow at low temperatures, including those found in refrigerators.

Question 6

A bacterium that grows optimally at pH 3 is classified as a(n):

Accepted Answer

Acidophile

Question 7

What happens to a bacterial cell placed in a hypertonic solution?

Accepted Answer

Water leaves the cell, causing plasmolysis.

Question 8

Which enzyme is responsible for converting superoxide radicals to hydrogen peroxide and oxygen in bacteria?

Accepted Answer

Superoxide dismutase (SOD)

Question 9

A facultative anaerobe is best described as an organism that:

Accepted Answer

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

Question 10

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

Accepted Answer

Zinc

Question 11

A culture medium that contains thioglycollate is best used for cultivating which type of bacteria?

Accepted Answer

Obligate anaerobes

Question 12

Which of the following best describes an autotroph?

Accepted Answer

An organism that uses CO$$_2 as $$its carbon source.

Question 13

A sample contains 1,000 bacteria. If the generation time is 20 minutes, how many bacteria will be present after 2 hours? Use $$N_f = (N_i)2^n.$$

Accepted Answer

64,000,000

Question 14

Which of the following best explains why food with a larger volume cools more slowly in a refrigerator, increasing the risk of bacterial growth?

Accepted Answer

Larger volumes retain heat longer, keeping the food in the danger zone for bacterial growth.

Question 15

Which of the following is NOT an essential macronutrient for microbial growth?

Accepted Answer

Manganese

Question 16

A microbiologist uses a spectrophotometer to measure bacterial growth. What is being measured?

Accepted Answer

The turbidity (cloudiness) of the culture, which correlates with cell density

Question 17

Which of the following best describes a fastidious bacterium?

Accepted Answer

A bacterium that requires many specific growth factors from its environment.

Question 18

Which of the following statements about nitrogen-fixing bacteria is correct?

Accepted Answer

They convert atmospheric N$$_2$$ into a form usable by living organisms.

Question 19

A microbiologist is culturing microaerophiles. Which of the following methods would be most appropriate?

Accepted Answer

Incubation in a candle jar to reduce oxygen and increase CO$$_2.$$

Question 20

Which of the following best describes the role of catalase in bacterial cells?

Accepted Answer

It converts hydrogen peroxide into water and oxygen.

Microbial Growth: Nutrition, Environmental Factors, and Measurement

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