The genus Bacterium was a taxon described in 1828 by Christian Gottfried Ehrenberg

Christian Gottfried Ehrenberg

Christian Gottfried Ehrenberg , German naturalist, zoologist, comparative anatomist, geologist, and microscopist, was one of the most famous and productive scientists of his time.- Early collections :...

. The type species was later changed from Bacterium triloculare to Bacterium coli (now Escherichia coli

Escherichia coli

Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

) as it was lost. In 1951 and then in 1954 it was recognised as a nomen generum rejiciendum, which means a rejected generic name, this also applied to its family Bacteriaceae.

This genus included non-spore forming rods whose relation to other species was obscure (a "taxonomy dumping group"). This is different to the genus Bacillus

Bacillus

Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

, whose members were spore forming rods (sensu Cohn 1872).

Species

Many species were placed under the genus. Given that the genus was abolished in the process of forming the Bacteriological Code there is no such thing as an official list of species present. These are those accepted by Breed and Conn in 1935:

• Bacterium radiobacter, then Agrobacterium tumefaciens, now Rhizobium radiobacter
• Bacterium aerogenes, now Aerobacter aerogenes
• Bacterium violaceum, now Chromobacterium violaceum
• Bacterium amylovorum, now Erwinia amylovora
• Bacterium zopfii, now Kurthia zopfii
• Bacterium monocytogenes, now Listeria monocytogenes
• Bacterium pneumoniae, now Klebsiella pneumoniae
  Klebsiella pneumoniae
  Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....