Gram stain

Gram stain
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.

Medical dictionary. 2011.

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  • Gram stain — Gram stain. См. окрашивание по Граму. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Gram stain — noun a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram s solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the… …   Useful english dictionary

  • gram stain — Staining technique for the initial identification of bacteria, devised in 1884 by the Danish physician Hans Christian Gram (1853–1938). The stain reveals basic differences in the biochemical and structural properties of a living cell. A slide… …   Universalium

  • Gram stain — A heat fixed bacterial smear is stained with crystal violet (methyl violet), treated with 3% iodine/potassium iodide solution, washed with alcohol and counterstained. The method differentiates bacteria into two main classes, Gram positive and… …   Dictionary of molecular biology

  • Gram stain — noun see Gram s stain …   New Collegiate Dictionary

  • Gram stain — noun Medicine a staining technique for the preliminary distinction of bacteria between two categories (Gram positive and Gram negative). Origin C19: named after the Danish physician Hans C. J. Gram …   English new terms dictionary

  • Gram stain — A differential staining procedure that divides bacteria into gram positive and gram negative groups based on their ability to retain crystal violet when decolorized with an organic solvent such as ethanol …   Dictionary of microbiology

  • gram stain test — A laboratory test for symptoms of gonorrhea, universally used, and considered to be practically conclusive, certainly so when the objective symptoms are present. Peterson v Widule, 157 Wis 641, 147 NW 966. granage (gran aj). Same as grainage …   Ballentine's law dictionary

  • Gram staining — (or Gram s method) is an empirical method of differentiating bacterial species into two large groups (Gram positive and Gram negative) based on the chemical and physical properties of their cell walls.cite book | last = Bergey | first = David H.… …   Wikipedia

  • 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 (called peptidologlycan). The Gram positive bacteria include… …   Medical dictionary

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