- Gram staining is a method of differentiating bacterial species into two large groups (gram-positive and gram-negative).
- Gram staining differentiates bacteria by the chemical and physical properties of their cell walls by detecting peptidoglycan, which is present in a thick layer in gram-positive bacteria.
- In a Gram stain test, gram-positive bacteria retain the crystal violet dye, while a counterstain (commonly safranin) added after the crystal violet gives all gram-negative bacteria a red or pink coloring.
Gram staining
