25 terms


Its function is to impart its color to all
primary stain
establish a color contrast
decolorizing agent
has a contrasting color to that of the primary stain
This is the final reagent, used to stain red those cells that have been previously decolorized
The best Gram stained preparations are made with fresh cultures, that is, not older than
24 hours
some cells will appear purple,
while others will appear red.
Crystal violet, Gram's iodine, 95% ethyl alcohol, and 0.25% safranin.
Gram stain
(substance that combines with the dye to form an insoluble compound
a dilute aqueous solution
Gram's iodine
used in Decolorization in gram step
95% ethanol. (ethyl alcohol)
used Counterstain in gram step
0.25% safranin
Very few bacteria are acid-fast
genera Mycobacterium and Nocardia
the result of having
cell walls with a high content of waxes and other complex lipids
resistant to drying and to many disinfectants
Primary stain of Acid Fast
carbo I fuchsin
Decolorization of Acid Fast
acid-alcohol (I % Hel in 70% ethanol).
Counterstain of Acid Fast
methylene blue
Resulting colors of Acid-Fast
red = acid-fast
blue = non-acid-fast
Primary stain of Spore Stain
malachite green
Counterstain of Spore Stain
0.5% safranin
Spore Stain results
Spores are green
Vegetative cells are red
This violet stain is used first and stains all cells purple
Crystal Violet
killing agent, increases the cells' affinity for a stain.
Gram's Iodine
serves a dual function as a protein dehydrating agent and as a lipid solvent.
Ethyl Alcohol (ethanol), 95%