Staining

Staining

I Basic dyes:
A. Positive ion
B. Attracted to negatively charged bacteria
C. types
1.Crystal violet
2. methylene blue
3. malachite green
4. safranin
D. used more often than acidic dyes

II Acidic dyes:
A. stains the background, not the bacteria
B. used in negative staining
C. types
1. eosin
2. acid fuchsin
3. nigrosin
III Differential stains: differentiates between different cell types
A. gram positive
1. CV-I complex: when the crystal violet and iodine make crystals inside the cell wall and then the cell wall keeps the color in.
2. thicker peptidoglycan wall in cells
3. killed easily by antibiotics because antibiotics prevent the proteins…
4. create endospores
5. Staphylococcus
6. has teichoic acids
7. 2 flagellar rings in basal body
B. gram negative
1. lipopolysaccharide wall with thin peptidoglycan layer lets crystal violet dye back out after alcohol wash because the alcohol was disrupts the lipopoly layer.
2. more resistant to antibiotics because of lipopolysaccharide layer
3. E. coli
4. no teichoic acid
5. 4 flagellar rings in basal body
C. acid fast
1. binds only to those cells with waxy material on cell walls
2. Mycobacterium (tuberculosis, leprae)
3. Nocardia
4. red dye: carbolfuchsin
5. Heat is needed for first red dye, then wash with acid/alcohol and add methylene blue.
6. acid fast stains show up as red, non acid fast show up as blue.


IV Special Stains
A. Negative: used to show capsules. Capsules indicate virulence
B. Endospore: used to show endospores. Malachite green then safranin
C. Flagella: used to show flagella
1. tedius
2. uses mordant to swell flagella, several applications
3. followed by carbolfuchsin