N: 1. – Gram-positive (adj): gram-positive = holding the purple dye when stained by Gram’s stain —used chiefly of bacteria. First Known Use of gram-positive: 1907.
– bacterium (n): New Latin, from Greek baktērion staff. First Known Use of bacterium: 1835. Plural: bacteria.
- Generally used in plural: Gram-positive bacteria.
2. 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).
3. The Gram-positive bacteria include staphylococci (“staph”), streptococci (“strep”), pneumococci, and the bacterium responsible for diphtheria (Cornynebacterium diphtheriae) and anthrax (Bacillus anthracis).
4. 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.
OV: gram-positive bacterium
S: TERMIUM PLUS – https://bit.ly/2JFtLUj (last access: 2 November 2019)