Robert Koch won the Nobel Prize in Physiology or Medicine in 1905. The Nobel committee specifically honored his investigations and discoveries concerning tuberculosis, rather than awarding him for all of his bacteriological work as a whole.
Koch identified the bacterium that causes tuberculosis in 1882 and showed how it could be isolated and studied. His work helped establish that particular microorganisms cause particular diseases, strengthening the germ theory of disease and transforming medical research.
Koch also made major contributions to the study of anthrax and cholera, developed laboratory methods for growing and identifying microbes, and formulated influential principles later known as Koch’s postulates. A common mix-up is to assume that his Nobel Prize recognized his discovery of the cholera bacterium; that discovery was important, but tuberculosis was the stated basis for the 1905 award.