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What is stained in a negative stain?
Background, not the cell
Common dyes used?
Nigrosin or India Ink
Why is Nigrosin useful?
Large colloidal particles can’t enter cell → clear outline.
What pH makes Nigrosin negatively charged?
pH 7
Is heat used in negative staining?
No, avoids distortion
Best bacteria type to view with this method?
Coccobacilli or short rods.
What kind of stain is it (simple or differential)?
Simple
Chromophore charge in acidic stain?
Negative
Why does background become dark?
Acidic dye repelled by cell → stains background.
Main benefit of no heat-fixing?
Bacteria stay alive shape-wise; less shrinking.