German bacteriologist who in the course of extensive immunological studies (1886–90) discovered a naturally occurring substance in the blood—now known as complement—that is capable of destroying bacteria. He also devised methods of studying anaerobic bacteria.

The brother of the Nobel Prize-winning chemist Eduard Buchner (Buchner, Eduard), he was educated at the Universities of Munich and Leipzig (M.D., 1874). After serving as a physician for the Bavarian army in the 1870s, Buchner taught at the University of Munich from 1880 until his death. He became professor of hygiene and director of the Hygienics Institute in 1894.

Buchner was one of the first to note that a substance in blood serum, alexin, could destroy bacteria. The substance, renamed complement by the immunologist Paul Ehrlich, is now known to be part of the complement system, which consists of about 20 proteins that act together to eliminate infectious organisms from the body. Buchner wrote Die ätiologische Therapie und Prophylaxis der Lungentuberculose (1883; “The Etiological Treatment and Prevention of Tuberculosis”), and several of his lectures were published during his lifetime.