Actinomyces (from Greek "actis" ray

Actinomyces (from Greek "actis" ray, beam and "mykes", fungus) is a genus of the actinobacteria class of bacteria. They are all gram-positive. Actinomyces are facultatively anaerobic (except A. meyeri, a strict anaerobe). All species 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.[1] The aspect of these colonies initially led to the incorrect assumption that the organism was a fungus and to the name "Actinomyces" or ray fungus.

Actinomyces are known for causing disease in humans, and for the important role they play in soil ecology. They produce a number of enzymes that help degrade organic plant material, lignin, and chitin. As such, their presence is important in the formation of compost. Some species have been found as part of the healthy vaginal microbiota.[2]