They are known for the important role they play in soil ecology; they produce a number of enzymes that help degrade organic plant material, lignin, and chitin.

Clinical laboratories do culture and isolate them, but a negative result does not rule out infection, because it may be due simply to reluctance to grow in vitro.

Phylogenetic trees based on 16S ribosomal RNA (16SrRNA) sequences have shown that the genus Actinomyces is quite diverse, exhibiting polyphyletic branching into several clusters.

The genera Actinomyces and Mobiluncus form a monophyletic clade in a phylogenetic tree constructed using RpoB, RpoC, and DNA gyrase B protein sequences.

This clade is also strongly supported by a conserved signature indel consisting of a three-amino-acid insertion in isoleucine tRNA synthetase found only in the species of the genera Actinomyces and Mobiluncus.

[11] Actinomyces species have also been shown to infect the central nervous system in a dog "without history or evidence of previous trauma or other organ involvement.

[13] Actinomycosis may be considered when a patient has chronic progression of disease across tissue planes that is mass-like at times, sinus tract development that may heal and recur, and refractory infection after a typical course of antibiotics.