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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.
Unlike negative staining, positive staining uses basic dyes to color the specimen against a bright background. While chromophore is used for both negative and positive staining alike, the type of chromophore used in this technique is a positively charged ion instead of a negative one. The negatively charged cell wall of many microorganisms ...
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]
Uranyl acetate is extensively used as a negative stain in electron microscopy. [3] Most procedures in electron microscopy for biology require the use of uranyl acetate. Negative staining protocols typically treat the sample with 1% to 5% aqueous solution.
Negative staining has higher resolution but can only identify molecules that would be recognizable if they are standing alone. When used in immune electron microscopy, negative staining implants a small particle into the specimen, better resolving structures within it.
The Gram stain is used by microbiologists to place bacteria into two main categories, Gram-positive (+) and Gram-negative (-). Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and Gram-negative bacteria have a thin layer of peptidoglycan.
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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 ...