Gram stainGram stain
also Gram's stain
A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranin. Because of differences in cell wall structure, gram-positive bacteria retain the violet stain whereas gram-negative bacteria do not. Also called Gram's method.
Origin of Gram stainAfter Hans Christian Joachim Gram, (1853–1938), Danish physician.
gram-positive anthrax bacteria