Gram-positive bacteria

Bacteria that give a positive result in the Gram stain test

Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall which retains the stain, unlike the thin layer of peptidoglycan in gram-negative bacteria that does not retain the stain. Gram-positive bacteria retain the crystal violet stain used in the test, resulting in a purple color when observed through an optical microscope.

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