Preparation of Smears & Simple Staining
Direct Stain
A simple stain that stains baceria
Which bacterium is on solid medium?
Bacillus, Pseudomonas...
Chemically Fix
Cover the smear with 95% methanol for 1 minute ***denatures proteins, coagulated proteins will allow specimen to stick to slide***
Heat-Fix
Dry smear is passed through a Bunsen burner flame several times ***used to kill bacterial cells & to preserve with minimal shrinkage & damage ; also used to stick to the slide***
Bacteria can be seen without staining. Why then was Koch's recommendation for fixing & staining important for microbiology?
Fixing & staining allows bacteria to be saved, re-examined, & shared for study
In heat fixing, what would happen if too much heat was applied?
It would damage & dehydrate the cells causing distortion in shape
Of what value is a simple stain?
Its a fast observation to determine morphology & arrangement of bacteria
Do not fix until smears are completely dry. Why?
May denature the smear
Simple Stain
Use only one stain
Can dyes other than methylene blue be used for direct staining?
Yes. Crystal violet, safranin, basic fuchsin - because they're all positive charges
How would pH of a stain affect the staining of bacteria?
pH determines the bacteria's charge