Question 1

Which of the following correctly identifies the primary and secondary stains used in Gram staining?

Accepted Answer

Primary: Crystal violet; Secondary: Iodine

Question 2

A bacterial sample is subjected to acid-fast staining. Which color will acid-fast positive bacteria appear under the microscope?

Accepted Answer

Red

Question 3

Which statement best describes the difference between selective and differential media?

Accepted Answer

Selective media inhibit the growth of certain bacteria, while differential media allow visualization of differences between bacteria.

Question 4

MacConkey agar is used in the lab. Which of the following best describes its properties?

Accepted Answer

It is both selective and differential.

Question 5

A blood agar plate shows clear zones around bacterial colonies. What type of hemolysis is this?

Accepted Answer

Beta hemolysis

Question 6

After adding iodine to a starch agar plate, a clear zone appears around a bacterial colony. What does this indicate about the bacterium?

Accepted Answer

It produces amylase and hydrolyzes starch.

Question 7

In an OF-glucose test, a bacterium produces a blue color in both aerobic and anaerobic tubes. What does this result indicate?

Accepted Answer

The bacterium does not metabolize glucose and the medium is alkaline.

Question 8

Which of the following best defines a competent cell in bacterial transformation?

Accepted Answer

A cell that can take up foreign DNA from its environment.

Question 9

Ampicillin is used in a bacterial transformation experiment. What is its role?

Accepted Answer

It selects for bacteria that have taken up the plasmid with the resistance gene.

Question 10

Why will competent cells alone not grow on an amp-agar plate in a transformation experiment?

Accepted Answer

They lack the ampicillin resistance gene.

Question 11

What is the intended purpose of the Ames test?

Accepted Answer

To determine if a chemical can induce mutations.

Question 12

On an Ames test plate, if colonies grow around one of the chemicals, what does this indicate?

Accepted Answer

The chemical induced mutations that allowed growth.

Question 13

In the OF-glucose test, what does a yellow color change in both aerobic and anaerobic tubes indicate?

Accepted Answer

The bacterium ferments glucose.

Question 14

Which of the following is the correct formula for calculating the mutation rate in the Ames test?

Accepted Answer

$$\frac{	ext{Number of revertant colonies}}{	ext{Total number of cells plated}}$$

Question 15

If no colonies grow on a plate after UV radiation in the Ames test, what does this most likely indicate?

Accepted Answer

UV radiation was lethal to the bacteria.

Question 16

Which stain is used as the primary stain in endospore staining?

Accepted Answer

Malachite green

Question 17

A sample is tested for endospores. If endospores are present, which color will they appear after staining?

Accepted Answer

Green

Question 18

Which of the following media is both selective and differential?

Accepted Answer

EMB agar

Question 19

A bacterium is plated on blood agar and shows no change in the medium. What type of hemolysis is this?

Accepted Answer

Gamma hemolysis

Question 20

During bacterial transformation, which phenotype will competent cells gain if the transformation is successful and the plasmid contains a gene for ampicillin resistance?

Accepted Answer

Ability to grow on amp-agar plates

Microbiology Lab Study Guide: Staining, Media, Metabolism, Transformation, and Mutation

Study Guide - Practice Questions

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