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Gram Staining
Tests whether the cell is gram positive or gram negative
Gram Positive
Thick peptidoglycan
Tehoic acids
Purple/Pink results
-Now Draw-
Gram Negative
Thinner peptidoglycan
Has Porins
E.Coli is an example
Outermembrane has LPS
-Now Draw-
Why does knowing whether a cell is gram positive or gram negative help?
A thicker peptidoglycan means harder entry for the antibiotic so it’s more resistant
Can all bacteria be classified with gram staining?
No!
Gram Stain Sequence
Crystal Violet: Primary stain. Both controls begin purple.
Gram’s iodine: Stabilizes color complex
Decolorizer: mixture of acetone and alcohol
Safranin: counterstain
Why are Gram-Positive envelopes purple?
Retains the crystal violet-iodine complex because of the hick peptidoglycan
Why are Gram-Negatives pink?
Loses the primary complex, then takes up safranin