Which German botanist classified bacteria into genera such as Bacillus in 1872?

Ferdinand Cohn classified bacteria into genera such as Bacillus in 1872. His influential system grouped bacteria by visible form and included six genera: Micrococcus, Bacterium, Bacillus, Vibrio, Spirillum, and Spirochaeta.

Cohn was a German botanist whose work helped establish bacteriology as a systematic scientific field. He studied bacterial shapes, life cycles, and resistant resting stages, and argued that bacteria were living organisms rather than merely chemical products of decay.

The classification was an important historical milestone, but it was not the modern bacterial taxonomy. Nineteenth-century scientists relied heavily on microscopy and morphology because they could not compare organisms by genetics or molecular traits. Many of Cohn’s groupings were later revised, while the genus name Bacillus remains in use.

A common mix-up is Ernst Haeckel, who also proposed broad classifications of microscopic life. Matthias Schleiden and Julius Sachs were major botanists, but neither is the canonical answer to this question.