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Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria.
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 that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an outer ...
A Gram stain of mixed Staphylococcus aureus (S. aureus ATCC 25923, gram-positive cocci, in purple) and Escherichia coli (E. coli ATCC 11775, gram-negative bacilli, in red), the most common Gram stain reference bacteria. Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups ...
It is known in medicine as Gentian violet (or crystal violet or pyoctanin(e) [1]) and is the active ingredient in a Gram stain, used to classify bacteria. It is used as a pH indicator, with a range between 0 and 1.6. The protonated form (found in acidic conditions) is yellow, turning blue-violet above pH levels of 1.6. [4]
Another factor in stain removal is the fact that stains can sometimes comprise two separate staining agents, which require separate forms of removal. A machine oil stain could also contain traces of metal, for example. [1] Also of concern is the color of the material that is stained. Some stain removal agents will not only dissolve the stain ...
Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and Gram-negative bacteria have a thin layer of peptidoglycan. Gram-positive bacteria retain the crystal violet stain used in the test, resulting in a purple color when observed through an optical microscope.
Examples include the malachite green counterstain to the fuchsine stain in the Gimenez staining technique and the eosin counterstain to haematoxylin in the H&E stain. [1] In Gram staining, crystal violet stains only Gram-positive bacteria, and safranin counterstain is applied which stains all cells, allowing the identification of Gram-negative ...
A Ziehl–Neelsen stain is an acid-fast stain used to stain species of Mycobacterium tuberculosis that do not stain with the standard laboratory staining procedures such as Gram staining. This stain is performed through the use of both red coloured carbol fuchsin that stains the bacteria and a counter stain such as methylene blue .