Koch, Robert (1843–1910), a German physician and bacteriologist. Koch was awarded the 1905 Nobel Prize in physiology or medicine for developing a test used in diagnosing tuberculosis. He isolated the bacilli causing anthrax (1876), tuberculosis (1882), and Asiatic cholera (1883). Koch developed a vaccine for treating anthrax (1883) and rinderpest (1896).

Koch developed a method for determining whether a particular bacterium causes a particular disease. His method involved the use of four rules, now called Koch's postulates: (1) the bacteria must be present in every case of the disease, (2) the bacteria must be capable of being isolated and cultured, (3) the bacteria must be able to produce disease in a healthy animal, (4) the bacteria recovered from the diseased animal must be proved to be the same as the bacteria that caused the original disease.

Koch also devised methods for obtaining cultures of bacteria by using media such as agar and gelatin and was the first to stain bacteria with aniline dyes to make them easier to detect under a microscope.

Koch received his medical degree from the University of Göttingen in 1866. He made his first discoveries while practicing medicine in Wollstein, 1872–80. In 1880 he was appointed to a position in the Imperial Health Office, Berlin. Koch was appointed a professor of hygiene and bacteriology at the University of Berlin and director of the Institute of Hygiene in 1885. In 1891 he became director of the Institute for Infectious Diseases.