Question 1

Which of the following actions should you take immediately if you spill a strong acid on your skin during a microbiology lab?

Accepted Answer

Rinse the affected area with copious amounts of water for at least 15 minutes.

Question 2

If the ocular lens of a microscope has a magnification of $$10	imes$$ and the high power objective lens has a magnification of $$40	imes$$, what is the total magnification achieved?

Accepted Answer

$$400	imes$$

Question 3

Which part of the microscope is best used to control the amount of light entering the objective lens?

Accepted Answer

Iris diaphragm

Question 4

What is the relationship between the field of vision and the magnifying power of the objective lens?

Accepted Answer

As magnifying power increases, field of vision decreases.

Question 5

Which bacterial shape is best described as spherical?

Accepted Answer

Cocci

Question 6

Which of the following is a blue-green bacterium commonly identified in lab slides?

Accepted Answer

Oscillatoria

Question 7

Which of the following is a key difference between yeast and mold?

Accepted Answer

Yeasts reproduce by budding, molds reproduce by spore formation.

Question 8

Which step in the Gram stain procedure is responsible for differentiating between Gram-positive and Gram-negative bacteria?

Accepted Answer

Decolorization with alcohol or acetone

Question 9

Why are basic dyes such as methylene blue used for staining bacterial cells?

Accepted Answer

Because bacterial cell walls are negatively charged and attract the positively charged dye ions.

Question 10

What is the main function of a bacterial capsule?

Accepted Answer

To protect against phagocytosis and desiccation

Question 11

Which genus of bacteria is stained by the acid-fast method due to the presence of mycolic acid in their cell walls?

Accepted Answer

Mycobacterium

Question 12

During the Schaeffer-Fulton spore stain, which dye is used to stain the endospores?

Accepted Answer

Malachite green

Question 13

When preparing a smear from a solid culture, which step is necessary before staining?

Accepted Answer

Add a drop of water to the slide and mix the bacteria into it.

Question 14

Why is heat fixing a bacterial smear important before staining?

Accepted Answer

It kills the bacteria and adheres them to the slide.

Question 15

Which of the following best describes the growth pattern of a facultative anaerobe in thioglycollate broth?

Accepted Answer

Growth throughout the tube, but denser at the top.

Question 16

What is the typical concentration of agar in a solid medium and in a semi-solid motility medium, respectively?

Accepted Answer

Solid: $$1.5\%$$, Semi-solid: $$0.4\%$$

Question 17

Which of the following is a source of contamination in the microbiology lab?

Accepted Answer

Touching the agar with ungloved hands

Question 18

Why are agar plates incubated upside down?

Accepted Answer

To prevent condensation from dripping onto the colonies.

Question 19

During quadrant streaking, where should the label be written on an agar plate?

Accepted Answer

On the bottom of the plate

Question 20

Which of the following steps helps prevent air contamination when inoculating an agar plate?

Accepted Answer

Flaming the loop and quickly covering the plate

Microbiology Lab Exam 1 Study Guide: Microscopy, Staining, and Basic Techniques

Study Guide - Practice Questions

Study Guide - Flashcards