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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 ...
Both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of teichoic acids in the cell wall. Some of ...
In Berlin, in 1884, Gram developed a method for distinguishing between two major classes of bacteria. [1] This technique, known as Gram staining, continues to be a standard procedure of medical microbiology. This work gained Gram an international reputation. The staining method later played a major role in classifying bacteria. Gram was a ...
Bacteria within the Deinococcota group may also exhibit Gram-positive staining behavior but contain some cell wall structures typical of Gram-negative organisms. Imbedded in the Gram-positive cell wall are polyalcohols called teichoic acids, some of which are lipid-linked to form lipoteichoic acids.
As a model organism, B. subtilis is commonly used in laboratory studies directed at discovering the fundamental properties and characteristics of Gram-positive spore-forming bacteria. [29] In particular, the basic principles and mechanisms underlying formation of the durable endospore have been deduced from studies of spore formation in B ...
Simple Staining is a technique that only uses one type of stain on a slide at a time. Because only one stain is being used, the specimens (for positive stains) or background (for negative stains) will be one color. Therefore, simple stains are typically used for viewing only one organism per slide. Differential staining uses multiple stains per ...
Some bacteria have cell wall structures that are neither classically Gram-positive or Gram-negative. This includes clinically important bacteria such as mycobacteria which have a thick peptidoglycan cell wall like a Gram-positive bacterium, but also a second outer layer of lipids. [80]
They generally stain gram-positive, but as well as Bacillus, are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages. [11] The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle.