GRAM STAINING

INTRODUCTION:
Gram staining is a method of differentiating bacterial species into two large groups: gram positive and gram negative.

OBJECTIVES:
1. Differentiate yogurt bacteria (Streptococcus and Lactobacillus)
2. Relate the staining procedure with the structure of the cells.

MATERIAL:
- Slide
- Tongs
- Cover slip
- Needle
- Gram stain: crystal violet, iodine and safranin
- Decolorize reagenti: ethanol 96%
- Yogurt
- Microscope

PROCEDURE:
1. Fix a piece of yogurt
2. Add crystal violet during 1 minute and 30 seconds
3. Add water
4. Add Lugol during 1 minute
5. Add water
6. Add ethanol
7. Add safranin during 1 minute
8. Add water