Actinomyces

Actinomyces is a genus of the Actinobacteria class of bacteria. They are all gram-positive. Actinomyces species are facultatively anaerobic (except A. meyeri, an obligate anaerobe), and they grow best under anaerobic conditions. Actinomyces species may form endospores, and, while individual bacteria are rod-shaped, Actinomyces colonies form fungus-like branched networks of hyphae. The aspect of these colonies initially led to the incorrect assumption that the organism was a fungus and to the name Actinomyces, "ray fungus" (from Greek actis, ray, beam and mykes, fungus).