or  Koch bacillus  n :  a bacillus of the genus Mycobacterium (M. tuberculosis) that causes human tuberculosis
 
Koch, (Heinrich Hermann) Robert (1843-1910), German bacteriologist. Koch is usually hailed as the founder of modern bacteriology. He is responsible for devising or adapting many of the basic principles and techniques (particularly staining methods) of bacteriology. He is most famous for isolating and obtaining in 1876 a pure culture of the bacterium (Bacillus anthracis) that causes anthrax, for discovering the cholera vibrio (Vibrio cholerae) in 1883, and for identifying and isolating the tubercle bacillus (Mycobacterium tuberculosis) in 1882. Koch published an epochal work on the etiology of traumatic infectious disease in 1878, and was the first (in 1887) to demonstrate that a specific microorganism is the cause of a specific disease. In 1890 he introduced tuberculin for the diagnosis of tuberculosis. Koch's postulates were first described in 1882 and then elaborated upon in 1884. The Koch-Weeks bacillus was discovered by Koch in 1883, and he described the Koch phenomenon in 1891. Koch was awarded the Nobel Prize for Physiology or Medicine in 1905.
 
   
 
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