Gram's stainmedical dictionary

<microbiology, technique> A method for differential staining of bacteria; smears are fixed by flaming, stained in a solution of crystal violet, treated with iodine solution, rinsed, decolorised, and then counterstained with safranin O.

Gram-positive organisms stain purple black and Gram-negative organisms stain pink; useful in bacterial taxonomy and identification, and also in indicating fundamental differences in cell wall structure.

(05 Mar 2000)