Gram stain

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Gram stain

 (grăm) also Gram's stain (grămz)
n.
A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranin. Because of differences in cell wall structure, gram-positive bacteria retain the violet stain whereas gram-negative bacteria do not. Also called Gram's method.

[After Hans Christian Joachim Gram (1853-1938), Danish physician.]
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Noun1.Gram stain - a staining technique used to classify bacteria; bacteria are stained with gentian violet and then treated with Gram's solution; after being decolorized with alcohol and treated with safranine and washed in water, those that retain the gentian violet are Gram-positive and those that do not retain it are Gram-negative
staining - (histology) the use of a dye to color specimens for microscopic study