Hanging-drop and wet-mount preparations

Week 1 – Review Sheet

Exercise 1: Hanging-drop and wet-mount preparations

1. How does true motility differ from Brownian movement?

2. What morphological structure is responsible for bacterial motility?

3. Why is a wet preparation discarded in disinfectant solution or biohazard container?

4. What is the value of a hanging-drop preparation?

5. What is the value of a wet-mount preparation?

Exercise 2: Simple stains

1. Define acidic and basic dyes. What is the purpose of each?

2. What is the purpose of fixing a slide that is to be stained?

3. Why are the specimens to be stained suspended in sterile saline or distilled water?

4. How does a stained preparation compare with a hanging drop for studying the morphology

and motility of bacteria?

5. List at least three types of bacteria whose names reflect their shapes and arrangements,

and state the meaning of each name.

Exercise 3: Gram stain

1. What is the function of the iodine solution in the Gram stain? If it were omitted, how would

staining results be affected?

2. What is the purpose of the alcohol solution in the Gram stain?

3. What counterstain is used? Why is it necessary? Could colors other than red be used?

4. What is the advantage of the Gram stain over a simple stain such as methylene blue?

5. In what kind of clinical situation would a direct smear report from the laboratory be of

urgent importance?