Stain, Gram
The Danish bacteriologist J.M.C. Gram (1853- 1938) devised a method of staining bacteria using a dye called crystal (gentian) violet. Gram’s method helps distinguish between different types of bacteria.
The gram-staining characteristics of bacteria are denoted as positive or negative, depending upon whether the bacteria take up and retain the crystal violet stain or not.
Gram-positive bacteria retain the color of the crystal violet stain in the Gram stain. This is characteristic of bacteria that have a cell wall composed of a thick layer of a particular substance (specifically, peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan).
The Gram-positive bacteria include staphylococci (“staph”), streptococci (“strep”), pneumococci, and the bacterium responsible for diphtheria (Cornynebacterium diphtheriae) and anthrax (Bacillus anthracis).
Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram’s method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (specifically, peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxin).
The Gram-negative bacteria include most of the bacteria normally found in the gastrointestinal tract that can be responsible for disease as well as gonococci (venereal disease) and meningococci (bacterial meningitis). The organisms responsible for cholera and bubonic plague are Gram-negative.
Read Also:
- Standard of care
1. A diagnostic and treatment process that a clinician should follow for a certain type of patient, illness, or clinical circumstance. Adjuvant chemotherapy for lung cancer is “a new standard of care, but not necessarily the only standard of care.” (New England Journal of Medicine, 2004) 2. In legal terms, the level at which the […]
- Stanolone
A semisynthetic analog of dihydrotestosterone.
- Stapes
A stirrup-shaped bone in the middle ear. The stapes transmits sound vibrations from the incus, another little bone in the middle ear, to the oval window adjacent to the inner ear. The stapes is the smallest bone in the body. Pronounced stay-peas. Stapes, a Late Latin word meaning stirrup, cannot have been a classical Latin […]
- Staph
Very commonly used shortened form of Staphylococcus, a very common and important group of bacteria. See Staphylococcal infection.
- Staph infection
A staph infection is an infection with a Staphylococcal bacteria.