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19 terms

Differential Stain

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Differential Stain
allow to detect differences between organisms or differences between parts of the same organism
gram stain
most commonly used differential stain in bacteriology
gram stain
differential stain in which a decolorization step occurs between the application of two basic stains
crystal violet
primary stain
iodine
mordant
iodine
to enhance crystal violate staining by forming a crystal-violet iodine complex
forms a crystal-violet iodine complex to enhance the crystal violet stain
what does iodine do after stained with crystal violet
decolorization
what is the most critical step in differential stain
gram negative cells
these cells are decolorized by the solution (alcohol or acetone) whereas gram positive are not
gram negative cells
__________________ can be colorized by the counterstain
safranin
what is the counterstain
gram negatives have higher lipid content because of the outer membrane and a thinner peptidoglycan layer than gram positive cell walls
gram negative cells are able to resist decolorization due to
alcohol
_________ in the decolorizer extracts the lipid making the gram negative wall more porous and incapable of retaining the crystal violet iodine complex thereby decolorizing it
thick peptidoglycan wall
the reason why gram positive cells are less susceptible to decolorization is because of
overdecolorize
leaving the alcohol on too long and get reddish gram positive cells
underdecolorize
produce purple gram negative cells
age
____ of the culture affects gram stain consistency
older gram positives
may lose their ability to resist decolorization and give an artificial gram - result
cell morphology, size and arrangement
gram stain allows