Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 76 (3), 111-8

Use of the Gram Stain in Microbiology

  • PMID: 11475313

Use of the Gram Stain in Microbiology

T J Beveridge. Biotech Histochem.


The Gram stain differentiates bacteria into two fundamental varieties of cells. Bacteria that retain the initial crystal violet stain (purple) are said to be "gram-positive," whereas those that are decolorized and stain red with carbol fuchsin (or safranin) are said to be "gram-negative." This staining response is based on the chemical and structural makeup of the cell walls of both varieties of bacteria. Gram-positives have a thick, relatively impermeable wall that resists decolorization and is composed of peptidoglycan and secondary polymers. Gram-negatives have a thin peptidoglycan layer plus an overlying lipid-protein bilayer known as the outer membrane, which can be disrupted by decolorization. Some bacteria have walls of intermediate structure and, although they are officially classified as gram-positives because of their linage, they stain in a variable manner. One prokaryote domain, the Archaea, have such variability of wall structure that the Gram stain is not a useful differentiating tool.

Similar articles

  • Gram Staining
    R Coico. Curr Protoc Microbiol Appendix 3, Appendix 3C. PMID 18770544.
    Named after Hans Christian Gram who developed the method in 1884, the Gram stain allows one to distinguish between Gram-positive and Gram-negative bacteria on the basis o …
  • Alternate Gram Staining Technique Using a Fluorescent Lectin
    RK Sizemore et al. Appl Environ Microbiol 56 (7), 2245-7. PMID 1697149.
    Fluorescence-labeled wheat germ agglutinin binds specifically to N-acetylglucosamine in the outer peptidoglycan layer of gram-positive bacteria. The peptidoglycan layer o …
  • The Response of Selected Members of the Archaea to the Gram Stain
    TJ Beveridge et al. Microbiology 142 ( Pt 10), 2887-95. PMID 8885405.
    Archaea possess a broader range of cell envelope structural formats than eubacteria and their cell walls do not contain peptidoglycan. Some archaea have only a single S-l …
  • The Gram Stain After More Than a Century
    A Popescu et al. Biotech Histochem 71 (3), 145-51. PMID 8724440. - Review
    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 mechani …
  • [Usefulness and Limit of Gram Staining Smear Examination]
    K Nagata et al. Rinsho Byori 58 (5), 490-7. PMID 20560458. - Review
    Gram staining is one of the most simple and inexpensive methods for the rapid diagnosis of bacterial and fungal infections. It yields results much faster than culture, an …
See all similar articles

Cited by 30 PubMed Central articles

See all "Cited by" articles

Publication types

LinkOut - more resources