born Dec. 11, 1843, Clausthal, Hannover
died May 27, 1910, Baden-Baden, Ger.
German physician.
As the first to isolate the anthrax bacillus, observe its life cycle, and develop a preventive inoculation for it, he was the first to prove a causal relationship between a bacillus and a disease. He perfected pure-culture techniques, based on Louis Pasteur 's concept. He isolated the tuberculosis organism and established its role in the disease (1882). In 1883 he discovered the causal organism for cholera and how it is transmitted and also developed a vaccination for rinderpest . Koch's postulates remain fundamental to pathology: the organism should always be found in sick animals and never in healthy ones; it must be grown in pure culture; the cultured organism must make a healthy animal sick; and it must be reisolated from the newly sick animal and recultured and still be the same. Awarded a Nobel Prize in 1905, he is considered a founder of bacteriology.