Staining Properties of Gram-Positive
and Gram-Negative Bacteria
Clinical Microbiology Review 147
GRAM REACTION CELL WALL STAINED BY COLOR IN GRAM STAIN
Gram positive Thick peptidoglycan layer with teichoic acid & lipoteichoic Crystal violet Purple
acid. Teichoic acid cross-links prevent decolorization in
Gram stain.
Gram negative Thin peptidoglycan layer covered with proteins, phospholipids, Safranin Pink
& lipopolysaccharides. Decolorizer causes ↑permeability of
lipid-rich cell wall. Primary stain (crystal violet) washes out.