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In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, and thus visible. This contrasts with positive staining, in which the actual specimen is stained.
A simple staining method for bacteria that is usually successful, even when the positive staining methods fail, is to use a negative stain. This can be achieved by smearing the sample onto the slide and then applying nigrosin (a black synthetic dye) or India ink (an aqueous suspension of carbon particles).
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 ...
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-negative bacteria will stain a pink color due to the thin layer of peptidoglycan. If a bacteria stains purple, due to the thick layer of peptidoglycan, the bacteria is a gram-positive bacteria. [4] In clinical microbiology numerous other staining techniques for particular organisms are used (acid fast bacterial stain for mycobacteria).
Immunofluorescence is a widely used example of immunostaining (using antibodies to stain proteins) and is a specific example of immunohistochemistry (the use of the antibody-antigen relationship in tissues). This technique primarily utilizes fluorophores to visualize the location of the antibodies, while others provoke a color change in the ...
The stain proved popular and in 1884 was used by Hans Christian Gram to stain bacteria. He credited Paul Ehrlich for the aniline-gentian violet mixture. [32] Grübler's gentian violet was probably very similar, if not identical, to Lauth's methyl violet, which had been used as a stain by Victor André Cornil in 1875. [33]
The Gimenez staining technique uses biological stains to detect and identify bacterial infections in tissue samples. Although largely superseded by techniques like Giemsa staining , the Gimenez technique may be valuable for detecting certain slow-growing or fastidious bacteria.