born Sept. 1, 1856, Kiev, Russian Empire
died Feb. 25, 1953, Brie-Comte-Robert, France
Russian microbiologist.
In studying the physiology of sulfur bacteria, he showed that the colourless ones oxidize hydrogen sulfide to sulfur and then to sulfuric acid in the absence of light (1887). He discovered two groups of microbes (1889-90), each involved in one step of nitrification (oxidation of ammonia to nitrites and nitrites to nitrates), and established a new genus for each. He also proposed new ways to study soil microorganisms, particularly those symbiotic with legumes.