Fig. 1.

The life cycle of filamentous actinomycetes based upon the model organism S. venezuelae . Development begins with the formation of one or two germ tubes from a spore. Following germination, mycelial outgrowth leads to the formation of vegetative mycelium. Transition from vegetative growth to aerial hyphae production occurs upon detection of signals, e.g. nutrient depletion. The aerial hyphae septate and mature into chains of pigmented spores that disperse, and the cycle can then begin again.