Question 1

Which of the following is the correct procedure for discarding used gloves in a microbiology lab?

Accepted Answer

Dispose of them in the biohazard waste container.

Question 2

What is the first action you should take in the event of a chemical spill emergency in the lab?

Accepted Answer

Notify your instructor and follow the emergency protocol.

Question 3

Which part of the microscope is responsible for adjusting the amount of light that reaches the specimen?

Accepted Answer

Iris diaphragm

Question 4

When carrying a microscope, which of the following is the correct technique?

Accepted Answer

Support the base with one hand and hold the arm with the other.

Question 5

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotes have a nucleus; prokaryotes lack a nucleus.

Question 6

What is the main purpose of performing a wet mount preparation in microbiology?

Accepted Answer

To observe living microorganisms and their motility.

Question 7

Which of the following is NOT a step in maintaining aseptic technique at the bench?

Accepted Answer

Leaving culture tubes open while working.

Question 8

A student observes that after Gram staining, all bacteria appear red. Which of the following is the most likely cause?

Accepted Answer

The crystal violet step was omitted.

Question 9

Where should you label a Petri plate before inoculation?

Accepted Answer

On the bottom (agar side) of the plate.

Question 10

Which colony isolation technique is most commonly used to obtain pure cultures from a mixed sample?

Accepted Answer

T-streak method

Question 11

You are asked to enumerate bacteria using a serial dilution and plate count. If you plate 0.1 mL from a $10^{-4}$ dilution and count 50 colonies, what is the original concentration of bacteria in the sample (CFU/mL)?

$	ext{CFU/mL} = \frac{	ext{Number of colonies}}{	ext{Volume plated (mL)}} 	imes 	ext{Dilution factor}$

Accepted Answer

$5 	imes 10^{5}$ CFU/mL

Question 12

Which of the following best describes selective media?

Accepted Answer

Media that inhibits the growth of certain microbes while allowing others to grow.

Question 13

What makes MacConkey agar both selective and differential?

Accepted Answer

It inhibits Gram-positive bacteria and differentiates lactose fermenters by color change.

Question 14

In an oxygen requirement test using fluid thioglycollate medium, what does growth only at the top of the tube indicate?

Accepted Answer

The organism is an obligate aerobe.

Question 15

Which indicator dye is commonly used in oxygen requirement media to detect the presence of oxygen?

Accepted Answer

Resazurin

Question 16

A sugar fermentation tube contains a Durham tube. What does the presence of gas in the Durham tube indicate?

Accepted Answer

The organism produces gas as a byproduct of sugar fermentation.

Question 17

What is the purpose of the MR-VP test in bacterial identification?

Accepted Answer

To differentiate bacteria based on their fermentation end products.

Question 18

Which medium is used to test for the presence of tryptophanase enzyme in bacteria, and what is a positive result?

Accepted Answer

SIM medium; red ring after adding Kovac's reagent

Question 19

A blood agar plate shows a clear, colorless zone around bacterial colonies. What type of hemolysis is this?

Accepted Answer

Beta hemolysis

Question 20

Which test is used to determine if a bacterium produces coagulase enzyme?

Accepted Answer

Coagulase test using plasma

BIO221 Lab Material Review: Microbiology Laboratory Techniques and Concepts

Study Guide - Practice Questions

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