Hans Gram. Portrait of Hans Christian Joachim Gram (1853-1938), Danish bacteriologist. In 1884 Gram invented a new staining technique. He discovered t

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Hans Gram. Portrait of Hans Christian Joachim Gram (1853-1938), Danish bacteriologist. In 1884 Gram invented a new staining technique. He discovered that some bacteria will retain an aniline-gentian violet after treatment with iodine solution and ethanol; others do not. The former are said to be Gram-positive, the latter are Gram-negative and the difference is due to the chemical structure of their membranes. The test is still important in the identification and classification of bacteria; penicillin will not attack Gram-negative microbes. Gram took up a clinical career and was appointed Professor of Medicine at Copenhagen in 1900.

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Keywords: ..., bacteriologist, christian, gram, hans, inventor, joachim, microscopist, portrait, portraits, stain, surname