释义 |
Gram's stain
Gram stain G0217500 (grăm) also Gram's stain (grămz)n. A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranin. Because of differences in cell wall structure, gram-positive bacteria retain the violet stain whereas gram-negative bacteria do not. Also called Gram's method. [After Hans Christian Joachim Gram (1853-1938), Danish physician.]ThesaurusNoun | 1. | Gram's stain - 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 gentian violet are Gram-positive and those that do not retain it are Gram-negativeGram method, Gram stain, Gram's method, Gram's procedurestaining - (histology) the use of a dye to color specimens for microscopic study |
Gram's stain
Gram's stain, laboratory staining technique that distinguishes between two groups of bacteria by the identification of differences in the structure of their cell walls. The Gram stain, named after its developer, Danish bacteriologist Christian Gram, has become an important tool in bacterial taxonomy, distinguishing between so-called gram-positive bacteria, which remain colored after the staining procedure, and gram-negative bacteria, which do not retain dye. In the staining technique, cells on a microscope slide are heat-fixed (killed) and stained with a basic dye, crystal violet, which stains all bacterial cells blue; then they are treated with an iodine-potassium iodide solution that allows the iodine to enter the cells and form a water-insoluble complex with the crystal violet dye. The cells are treated with alcohol or acetone solvent in which the iodine-crystal violet complex is soluble. Following solvent treatment, only gram-positive cells remain stained, possibly because of their thick cell wall, which is not permeable to solvent. After the staining procedure, cells are treated with a counterstain, i.e., a red acidic dye such as safranin or acid fuchsin, in order to make gram-negative (decolorized) cells visible. Counterstained gram-negative cells appear red, and gram-positive cells remain blue. Although the cell walls of gram-negative and gram-positive bacteria are similar in chemical composition, the cell wall of gram-negative bacteria is a thin layer sandwiched between an outer lipid-containing cell envelope and the inner cell membrane, whereas the gram-positive cell wall is much thicker, lacks the cell envelope, and contains additional substances, such as teichoic acids, polymers composed of glycerol or ribitol. The difference in reactivity between gram-positive and gram-negative bacteria is linked with differences in physiological properties of the two groups. Gram-positive bacteria are generally more sensitive to growth inhibition by dyes, halogens, many antibioticsantibiotic, any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms. Types of Antibiotics ..... Click the link for more information. , and to attack by phagocytosis (see endocytosisendocytosis , in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm surges forward to meet and surround the material and a depression forms within the cell wall. ..... Click the link for more information. ), and are more resistant to digestion by the enzymes pepsinpepsin, enzyme produced in the mucosal lining of the stomach that acts to degrade protein. Pepsin is one of three principal protein-degrading, or proteolytic, enzymes in the digestive system, the other two being chymotrypsin and trypsin. ..... Click the link for more information. and trypsintrypsin, enzyme that acts to degrade protein; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsin and chymotrypsin. ..... Click the link for more information. and enzymes in animal sera.Gram's stain[′gramz ‚stān] (microbiology) A differential bacteriological stain; a fixed smear is stained with a slightly alkaline solution of basic dye, treated with a solution of iodine in potassium iodide, and then with a neutral decolorizing agent, and usually counterstained; bacteria stain either blue (gram-positive) or red (gram-negative). Gram's stain
Gram's stain a stain taken up by the Gram-positive bacteria that differentiates these from bacteria which fail to take up the stain (Gram-negative types). The initial stain is crystal violet/iodine complex, and Gram-negative bacteria are decolorized with alcohol whilst Gram-positive bacteria retain a blue/purple colour.Gram's stainA stain used in microbiology to classify bacteria and help identify the species to which they belong. This identification aids in determining treatment.Mentioned in: Aminoglycosides, DiphtheriaGram's stain
Synonyms for Gram's stainnoun a staining technique used to classify bacteriaSynonyms- Gram method
- Gram stain
- Gram's method
- Gram's procedure
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