Lab Exercise 6B (Cell Morphology: Gram Stain and KOH Test)

Question 1

What kind of stain is the Gram stain? (make sure to use FRESH CELLS 24-48 hrs b/c as get old wall gets thinner)

Answer 1

Direct, Differential stain: a stain procedure that treats all cells the same but in the end have different appearances based on cell type

Question 2

What are the steps and the purpose of the steps for the Gram stain?

Answer 2

To determine the thickness of the cell wall

Question 3

What reagents are used? What purpose do the reagents serve in the staining procedure (ie: primary stain, destain, etc.)?

Answer 3

CRYSTAL VIOLET (primary stain) –> both show purple cells
GRAM’S IODINE (mordant) –> both show purple cells
ACETONE/ ALCOHOL (decolorizing agent)–> + purple cells/
- colorless
SAFRANIN (counterstain) –> + purple cells/ - pink cells

Question 4

What color do different cells or structures appear after the staining procedure? Why?

Answer 4

DATA: purple cells RESULT: + CONCL: the organism thick cell
wall
DATA: pink cells RESULT: - CONCLU: the organism has a thin
cell wall

Question 5

How does the KOH test work?

Answer 5

3% KOH (potassium hydroxide)
Mix up cells and lift up loop look for viscosity
DATA: vicous (snot) RESULT: + CONCLU: Thin cell wall
SNOT means the it’s the DNA since has thin cell wall
DATA: Not viscous (no snot) RESULT: - CONCLU: thick cell wall