Actinomyces is a genus of bacteria that belongs to the family Actinomycetaceae. The Actinomyces genus is composed of a diverse group of gram-positive, anaerobic, non-sporulating rods. While they are classified as bacteria, they have some characteristics that are similar to fungi.
The Actinomyces genus typically forms branching, filamentous structures that are often mistaken for fungal hyphae. They can also form complex networks of intertwined filaments that are called "mycelia" and can sometimes be mistaken for fungal mycelia. Additionally, Actinomyces have a tendency to form spore-like structures that can be confused with fungal spores.
However, unlike fungi, Actinomyces do not possess a cell wall containing chitin or other polysaccharides, and they do not produce any sexually-reproducing structures. Additionally, Actinomyces are not able to utilize organic carbon sources without the presence of living host cells, while fungi are able to do so.
In conclusion, Actinomyces are classified as bacteria, and they possess some characteristics that are similar to fungi. However, there are some key differences between the two, and these differences make it clear that Actinomyces belong in the bacterial domain.