Question 1

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that uses organic compounds as both an energy and carbon source.

Question 2

A bacterium is isolated from a deep-sea hydrothermal vent where temperatures reach 90$^\circ$C. Which term best describes its temperature preference?

Accepted Answer

Hyperthermophile

Question 3

Which of the following equations correctly represents the catalase reaction that detoxifies hydrogen peroxide?

Accepted Answer

$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 4

A microbiologist is culturing a bacterium that requires a large number of growth factors and cannot grow on a defined medium. What term best describes this organism?

Accepted Answer

Fastidious

Question 5

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species.

Question 6

A sample is taken from the Great Salt Lake and cultured. The organisms require 30% NaCl for growth. What term best describes these organisms?

Accepted Answer

Obligate halophiles

Question 7

Which of the following is a direct method for measuring microbial growth that does NOT require incubation?

Accepted Answer

Petroff-Hausser counting chamber

Question 8

A bacterial culture is in the stationary phase of growth. Which of the following best describes what is happening in the culture?

Accepted Answer

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

Question 9

Which of the following best describes the function of quorum sensing in biofilms?

Accepted Answer

It allows bacteria to coordinate gene expression based on population density.

Question 10

A clinical sample is streaked on MacConkey agar. Colonies appear pink. What does this indicate about the bacteria?

Accepted Answer

They are Gram-negative and ferment lactose.

Question 11

Which of the following is a reason why nitrogen fixation by bacteria is essential for life on Earth?

Accepted Answer

Most organisms cannot use atmospheric N$_2$ directly and rely on fixed nitrogen for amino acids and nucleotides.

Question 12

A bacterium is isolated from an acidic hot spring (pH 2, 70$^\circ$C). Which terms best describe its environmental preferences?

Accepted Answer

Acidophile and thermophile

Question 13

Which of the following best describes the function of a chemostat in microbial culture?

Accepted Answer

It maintains a continuous culture by supplying fresh medium and removing spent medium.

Question 14

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

Accepted Answer

Using an anaerobic jar with a chemical packet that removes O$_2$

Question 15

Which of the following best explains why endospores can survive in dry environments?

Accepted Answer

Endospores cease most metabolic activity and can survive without water.

Question 16

A bacterial population doubles every 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours?

Accepted Answer

$2^6 = 64$

Question 17

Which of the following is a trace element required in small amounts by microorganisms?

Accepted Answer

Zinc

Question 18

A patient develops a bloodstream infection after dental surgery. Which of the following best explains how dental plaque contributed to this infection?

Accepted Answer

Dental plaque is a biofilm that protects bacteria from the immune system and antibiotics, allowing them to enter the bloodstream.

Question 19

Which of the following best describes the difference between selective and differential media?

Accepted Answer

Selective media favor the growth of certain microbes, while differential media distinguish between microbes based on metabolic traits.

Question 20

A microbiologist uses a spectrophotometer to measure the turbidity of a bacterial culture. What is being measured?

Accepted Answer

The amount of light absorbed or transmitted by the culture, which correlates with cell density.

Microbial Nutrition and Growth: Study Notes for Microbiology Students

Study Guide - Practice Questions

Study Guide - Flashcards