"A genus of Gram-positive, facultatively anaerobic bacteria with rod-shaped and branching filamentous forms, which form part of the normal mucosal flora in mammals but may cause opportunistic infections. Also (in form actinomyces): a bacterium of this genus (also called ray fungus)", Late 19th cent. From scientific Latin Actinomyces, genus name from classical Latin actīno- + scientific Latin myces.
"A bacterium of an order of typically non-motile filamentous forms. They include streptomycetes, and were formerly regarded as fungi", 1920s (originally only in the plural): modern Latin, from Greek aktis, aktin- 'ray' + mukētes, plural of mukēs 'fungus'.
