Question 1

Which of the following best defines a pure culture in microbiology?

Accepted Answer

A culture in which all organisms are descendants of the same organism.

Question 2

What is the primary purpose of using aseptic technique during the transfer of microorganisms?

Accepted Answer

To prevent unwanted microorganisms from contaminating the culture.

Question 3

Which of the following is NOT a correct step in aseptically transferring inoculum from a broth culture to a sterile broth tube?

Accepted Answer

Place the inoculating loop on the benchtop after transfer.

Question 4

Which of the following best describes 'turbidity' in a broth culture?

Accepted Answer

A cloudy appearance throughout the broth.

Question 5

A student observes a red pigment diffusing throughout the agar medium from a bacterial colony. What type of pigment is this?

Accepted Answer

Water-soluble pigment

Question 6

Which of the following media would you use to isolate individual bacterial colonies from a mixed sample?

Accepted Answer

Agar plate

Question 7

Why is it important to allow the inoculating loop to cool before touching the inoculum?

Accepted Answer

To avoid killing the microorganisms with heat.

Question 8

Which of the following best describes the function of agar in microbiological media?

Accepted Answer

It acts as a solidifying agent.

Question 9

A student streaks a plate and observes isolated colonies in the third section. What does this indicate about the streak plate technique?

Accepted Answer

It successfully diluted the sample to isolate single colonies.

Question 10

Which of the following is the correct order for aseptically transferring inoculum from a slant tube to a sterile agar plate?

Accepted Answer

Sterilize loop, collect inoculum, streak plate, sterilize loop between each section.

Question 11

Which of the following best defines 'colony morphology'?

Accepted Answer

The visible characteristics of a colony such as form, elevation, margin, surface, and pigmentation.

Question 12

What is the main reason for cleaning your benchtop with Lysol before and after microbiology lab work?

Accepted Answer

To remove all life forms and prevent contamination.

Question 13

Which of the following is a correct definition of 'chromogenic' bacteria?

Accepted Answer

Bacteria that produce pigment.

Question 14

A broth tube shows a mass of organisms at the bottom but the rest of the broth is clear. What type of growth is this?

Accepted Answer

Sediment

Question 15

Which of the following is the correct disposal method for used gloves in the microbiology lab?

Accepted Answer

Red biohazard bin

Question 16

Which of the following equations best represents the process of binary fission in bacteria?

Accepted Answer

$$N_t = N_0$ 	imes 2^n$$

Question 17

Why is it important to label all cultures before incubation?

Accepted Answer

To ensure accurate identification of organisms after growth.

Question 18

Which of the following best describes a water-insoluble pigment produced by bacteria?

Accepted Answer

The pigment remains within the bacterial colony.

Question 19

A student observes a pellicle in a broth culture. What does this indicate about the bacteria?

Accepted Answer

The bacteria are forming a mass at the surface of the broth.

Question 20

Which of the following is the best definition of 'sterile medium'?

Accepted Answer

A medium that is free of all life forms.

Microbiology Lab 2 Study Guide

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