Q: Which equation correctly represents the catalase reaction that detoxifies hydrogen peroxide?

$$2H_2O_2 \xrightarrow{\text{catalase}} 2H_2O + O_2$

Question 1

Which of the following best describes a mesophile?

Accepted Answer

An organism that grows best at moderate temperatures, typically around 37°C

Question 2

Why is the pH of culture media often controlled in laboratory settings?

Accepted Answer

To minimize pH changes that could inhibit microbial growth

Question 3

A bacterium is found growing in a jar with a gas-generating packet that produces a low-oxygen, high-CO₂ environment. What is the most likely classification of this bacterium?

Accepted Answer

Capnophile

Question 4

Which equation correctly represents the catalase reaction that detoxifies hydrogen peroxide?

Accepted Answer

$$2H_2O_2 \xrightarrow{	ext{catalase}} 2H_2O + O_2$

Question 5

A food sample is placed in a refrigerator at 4°C. Which group of microbes is most likely to cause spoilage under these conditions?

Accepted Answer

Psychrotrophs

Question 6

Which of the following is a direct method for measuring microbial growth?

Accepted Answer

Plate count using serial dilution

Question 7

A bacterium that can survive but not use oxygen is classified as:

Accepted Answer

Aerotolerant anaerobe

Question 8

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

Accepted Answer

Salt causes plasmolysis by drawing water out of the cell

Question 9

Which of the following is NOT a chemical requirement for microbial growth?

Accepted Answer

Osmotic pressure

Question 10

A laboratory is working with a highly infectious airborne pathogen. Which biosafety level (BSL) is most appropriate?

Accepted Answer

BSL-3

Question 11

Which of the following best describes a biofilm?

Accepted Answer

A community of microorganisms encased in a slime or hydrogel matrix

Question 12

Which of the following is a function of phosphorus in microbial cells?

Accepted Answer

Component of DNA, RNA, and ATP

Question 13

A microbiologist wants to isolate a pure culture from a mixed sample. Which method should they use?

Accepted Answer

Streak plate method

Question 14

Which of the following media would you use to grow an obligate anaerobe?

Accepted Answer

Reducing media

Question 15

Which of the following equations correctly calculates the total number of cells after n generations, starting with a single cell?

Accepted Answer

$$	ext{Total cells} = 2^n$$

Question 16

Which of the following is a characteristic of complex media?

Accepted Answer

Contains extracts and digests of yeasts, meat, or plants

Question 17

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

Accepted Answer

Stationary phase

Question 18

Which of the following best explains why biofilms are medically significant?

Accepted Answer

They are 1000x more resistant to microbicides than planktonic cells

Question 19

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

Accepted Answer

Iron

Question 20

Which of the following is an example of a selective medium?

Accepted Answer

Bismuth sulfite agar

Chapter 6 Microbial Growth: Requirements, Culture, and Measurement

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