Staining

Article By:

Knaysi, Georges Department of Microbiology, Cornell University, Ithaca, New York.

Last reviewed:April 2019

DOI:https://doi.org/10.1036/1097-8542.650400

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• Stain (microbiology), published June 2014:Download PDF Get Adobe Acrobat Reader

The use of any colored, organic compound, usually called dye, to stain tissues, cells, cell components, cell contents, or microorganisms. Stains (dyes) are an important tool for biological researchers, particularly microbiologists. The stain (Fig. 1), or dye, may be natural or synthetic. The object stained is called the substrate. The small size and transparency of microorganisms and cells make them difficult to see even with the aid of a high-power microscope. Staining facilitates the observation of a substrate by introducing differences in optical density or in light absorption between the substrate and its surroundings or between different parts of the same substrate. In electron microscopy, and sometimes in light microscopy (as in the silver impregnation technique of staining flagella or capsules), staining is accomplished by depositing ultraphotoscopic particles of a metal, such as chromium or gold (the so-called shadowing process), on the substrate; or staining is done by treating the substrate with solutions of metallic compounds, such as uranyl acetate or phosphotungstic acid. See also: Cell (biology); Dye; Electron microscope; Microbiology; Microscope; Microtechnique; Tissue

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