Solid cultures of the producing strain grown on Bennett medium develop abundant mycelium and intense sporulation. Under these conditions biosynthesis of APHE antibiotics (APHE-1 to -3) is accomplished. Further studies show that APHE-3 is basically produced during spore formation and mostly present in spores, while APHE-1 and APHE-2 are the predominant antibiotics in the mycelium. APHE compounds are present in almost all streptomycetes tested, indicating a possible role in the life cycle of these microorganisms.