Corynebacterium (order Actinomycetales) A genus of Gram-positive bacteria, in which the cells tend to be irregular in shape, but are usually straight or slightly curved rods. They are chemo-organotrophic, and are found in a wide range of habitats. Some are pathogenic in animals (e.g. C. diphtheriae can cause diphtheria).

Corynebacterium (kŏ-ry-ni-bak-teer-iŭm) n. a genus of Gram-positive, mostly aerobic, nonmotile rodlike bacteria. C. diphtheriae (Klebs-Loeffler bacillus) the causative organism of diphtheria. It occurs in one of three forms: gravis, intermedius, and mitis.