Smear Prep, Simple, & Negative Staining Deck (Practical)

Question 1

Uniformly spread specimen on a glass slide for microscopic observation

Answer 1

What is a smear?

Question 2

The act of taking bacteria from culture (agar or broth) or clinical specimens, environmental samples, or food samples and spreading them on a slide for microscopic examination

Answer 2

What is smear preparation?

Question 3

What 3 qualities make for a good smear?

Answer 3

1) Even distribution
2) Not too thick
3) Not too thin

Question 4

Bacterial cells have { } charged components.

Answer 4

Negatively

Question 5

Crystal violet, safranin, methylene blue, and malachite green are basic, cationic dyes. What does this mean when referring to the charge?

Answer 5

Basic dyes are positively charged

Question 6

Congo red, India ink, and nigrosine are acidic, anionic dyes. What does this mean when referring to the charge?

Answer 6

Acidic dyes are negatively charged

Question 7

Why can’t acidic dyes stain bacterial cells?

Answer 7

Because the cells are negatively charged

Question 8

Basic dyes stain the { }, but not the background, and this process is referred to as { } staining.

Answer 8

1) Cell
2) Simple/positive

Question 9

Acidic dyes stain the { }, but not the cell, and this process is referred to as { } staining.

Answer 9

1) Background
2) Negative

Question 10

Why should you not heat-fix a negative-stained smear?

Answer 10

It will shrink and distort the capsule and other structures

Question 11

Simple staining looks at bacterial { }, i.e., shape, size, and arrangement. Negative staining looks at bacterial cell { }, i.e., capsules and spores.

Answer 11

1) Morphology
2) Structure