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Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is their cell envelope , which consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an ...
Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. [1] The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884. [2] Gram ...
Haemophilus influenzae (formerly called Pfeiffer's bacillus or Bacillus influenzae) is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37 °C. [1]
Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet during Gram staining, resulting in a purple color. Gram-negative bacteria have a thin peptidoglycan layer which does not retain the crystal violet, so when safranin is added during the process, they stain red.
The Gram stain, developed in 1884 by Hans Christian Gram, characterises bacteria based on the structural characteristics of their cell walls. [175] [75] The thick layers of peptidoglycan in the "Gram-positive" cell wall stain purple, while the thin "Gram-negative" cell wall appears pink. [175]
Chlamydia trachomatis is a gram-negative bacterium that can replicate exclusively within a host cell, making it an obligate intracellular pathogen. [3] Over the course of its life cycle, C. trachomatis takes on two distinct forms to facilitate infection and replication.
E. coli is a gram-negative, facultative anaerobe, nonsporulating coliform bacterium. [18] Cells are typically rod-shaped, and are about 2.0 μm long and 0.25–1.0 μm in diameter, with a cell volume of 0.6–0.7 μm 3. [19] [20] [21] E. coli stains gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane.
Fusobacterium is a genus of obligate anaerobic, Gram-negative, [2] non-sporeforming bacteria [3] belonging to Gracilicutes. Individual cells are slender, rod-shaped bacilli with pointed ends. [4] [5] Fusobacterium was discovered in 1900 by Courmont and Cade and is common in the flora of humans. [6] [7]