Gram'smethod

Gram's method (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 safranine. Gram-positive bacteria retain the violet stain; gram-negative bacteria do not.

  [After Hans Christian Joachim Gram (1853-1938), Danish physician.]

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