‖n. pl. [ NL. See Micro-, and Bacterium. ] (Biol.) In the classification of Cohn, one of the four tribes of Bacteria. [ 1913 Webster ]

☞ In this classification bacteria are divided into four tribes: 1. Spherobacteria, or spherical bacteria, as the genus Micrococcus. 2. Microbacteria, or bacteria in the form of short rods, including the genus Bacterium. 3. Desmobacteria, or bacteria in straight filaments, of which the genus Bacillus is a type. 4. Spirobacteria, or bacteria in spiral filaments, as the genus Vibrio. [ 1913 Webster ]

n. pl. A group of rod-shaped bacteria, some saprophytic or causing diseases.
Syn. -- mycobacterium. [ WordNet 1.5 ]