Actinomycetes are single-celled microorganisms. In the vegetative growth stage, the mycelium has no transverse septa and is in the state of multiple septa and single cells. The mycelium of actinomycetes consists of matrix mycelium, aerial mycelium and sporotrichum, among which matrix mycelium, also known as vegetative mycelium, grows in culture medium.

When the substrate mycelium grows to a certain stage, the aerial mycelium can grow into the air, and the aerial mycelium further differentiates to produce sporophytes and spores.