The Gram stain after more than a century

Biotech Histochem. 1996 May;71(3):145-51. doi: 10.3109/10520299609117151.


The Gram stain, the most important stain in microbiology, was described more than a century ago. Only within the past decade, however, has an understanding of its mechanism emerged. It now seems clear that the cell wall of Gram-positive microorganisms is responsible for retention of a crystal violet:iodine complex. In Gram-negative cells, the staining procedures damage the cell surface resulting in loss of dye complexes. Gram-positive microorganisms require a relatively thick cell wall, irrespective of composition, to retain the dye. Therefore, Gram-stainability is a function of the cell wall and is not related to chemistry of cell constituents. This review provides a chronology of the Gram stain and discusses its recently discovered mechanism.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Gentian Violet / chemistry*
  • Molecular Structure
  • Phenazines / chemistry*
  • Staining and Labeling*


  • Gram's stain
  • Phenazines
  • Gentian Violet