Christian Gottfried Ehrenberg, a German naturalist, zoologist, comparative anatomist, and geologist who had been appointed professor of medicine at Berlin University in 1827, had accompanied Humboldt through eastern Russia to the Chinese frontier in 1829.

After his return, he begins to concentrate his studies on microscopic organisms, which until then had not been systematically studied, and establishes the genus Bacterium, employing a term formed from the Greek word “bacterion,” signifying a rod.