Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses organic compounds for both energy and carbon.

Question 2

Why is oxygen deadly for obligate anaerobes?

Accepted Answer

They lack the enzymes to detoxify reactive oxygen species.

Question 3

A bacterium is found growing at the bottom of a test tube of thioglycollate broth. What is its likely oxygen requirement?

Accepted Answer

Obligate anaerobe

Question 4

Which toxic form of oxygen is produced during aerobic metabolism and is detoxified by the enzyme catalase?

Accepted Answer

Peroxide anion

Question 5

Nitrogen fixation is essential to life on Earth because:

Accepted Answer

It converts nitrogen gas into ammonia, which can be used by living organisms.

Question 6

Which of the following best describes a psychrophile?

Accepted Answer

A microbe that grows best at temperatures below 15°C.

Question 7

What is the main reason most cells die in the absence of water?

Accepted Answer

Water is needed to dissolve enzymes and nutrients for metabolism.

Question 8

Which type of medium would you use to isolate a bacterium that can grow in the presence of high salt concentrations?

Accepted Answer

Selective medium

Question 9

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

Accepted Answer

Serial dilution and viable plate count

Question 10

Which of the following best explains why biofilms are often more resistant to antibiotics than planktonic (free-living) bacteria?

Accepted Answer

The extracellular matrix of biofilms restricts penetration of antibiotics.

Question 11

A bacterium is classified as a facultative anaerobe. Which of the following best describes its growth in a test tube?

Accepted Answer

It grows throughout the tube but more densely at the top.

Question 12

Which equation correctly describes the calculation of bacterial population size after $n$ generations, starting from a single cell?

Accepted Answer

$N = 2^n$

Question 13

Which of the following is a real-life example of a synergistic microbial relationship?

Accepted Answer

Bacteria in the human gut producing vitamins that benefit the host.

Question 14

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

The number of new cells equals the number of dying cells.

Question 15

A microbiologist wants to culture an obligate anaerobe. Which of the following methods would be most appropriate?

Accepted Answer

Use of a GasPak anaerobic system.

Question 16

Which of the following is a trace element required by microbes?

Accepted Answer

Zinc

Question 17

Which of the following best explains why barophiles cannot survive at sea level?

Accepted Answer

Their enzymes denature at low pressure.

Question 18

Which of the following is an indirect method for measuring microbial growth?

Accepted Answer

Turbidity measurement using a spectrophotometer

Question 19

Which of the following statements about defined and complex media is correct?

Accepted Answer

Complex media contain nutrients of unknown exact composition.

Question 20

A scientist isolates a bacterium that grows best at pH 9. Which term best describes this organism?

Accepted Answer

Alkalinophile

Microbial Nutrition, Growth, and Culturing: Study Notes

Study Guide - Practice Questions