Definition: A unicellular prokaryotic microorganism that usually multiplies by cell division and has a cell wall that provides a constancy of form; they may be aerobic or anaerobic, motile or nonmotile, and free living, saprophytic, commensal, parasitic, or pathogenic.
[Mod. L. fr. G. baktērion, dim. of baktron, a staff]
See Also: Cyanobacteria