Question

What is the basis of differentiation in Gram stain?

How should a proper smear (emulsion) should look like in your slide?

If you properly Gram stain a human cell what color would it be? why?

What would happen if you use an old culture for gram-positive bacteria?

Answer 1

Gram staining is a special technique which is used to stain bacteria. It can differentiate the two major categories of bacteria: Gram positive and Gram negative. The Gram stain reaction affects on bacteria based on the biochemical and structural differences of their cell walls.

An effective smear should appear as a thin whitish layer or film after heat-fixing.

If I gram stain a human cell, there will be no color. Because the primary stain would be removed easily because the human cells do not have cell walls.

If I use an old culture for gram-positive bacteria (gram staining) then the old culture smears can cause cells to appear gram-negative (weak walls).