Gram stain

Gram Stain

Gram stain (pronunciation: /ɡræm/), also known as Gram's method, is a staining technique used in microbiology to differentiate bacterial species into two large groups: Gram-positive bacteria and Gram-negative bacteria. The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884.

Etymology

The term "Gram stain" is derived from the name of its inventor, Hans Christian Gram, a Danish bacteriologist. He developed this method while working in the morgue of the city hospital in Berlin in 1884. The word "stain" refers to the staining process used in the technique.

Procedure

The Gram stain procedure distinguishes between Gram-positive and Gram-negative groups by coloring these cells red or violet. Gram-positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. Gram-negative bacteria do not retain this violet stain and are instead colored red by the safranin counterstain.

Importance

The Gram stain is always the first step in the preliminary identification of a bacterial organism. While it doesn't provide definitive identification, it provides information about the properties of the bacterium, which can guide further testing and treatment decisions.

Related Terms

• Bacteria
• Microbiology
• Cell wall
• Peptidoglycan
• Gram-positive bacteria
• Gram-negative bacteria

External links

• Medical encyclopedia article on Gram stain
• Wikipedia's article - Gram stain

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