Gram staining is a method for staining samples of bacteria that differentiates between the two main types of bacterial cell wall.
Gram Staining a Step by Step Procedure
Inspect the slide under a microscope
- Gram positive organisms will appear blue-black or purple.
- Gram negative organisms will appear red.
As a rule of thumb (which has exceptions), Gram-negative bacteria are more dangerous as disease organisms, because their outer membrane acts as "camouflage"; the human body does not contain peptidoglycan and in fact produces an enzyme called lysozyme which attacks the open peptidoglycan layer of Gram-positive bacteria. Gram-positive bacteria are also much more susceptible to penicillin.