[Electron microscopic study of spore formation in Actinomadura verrucosospora]

The formation of spores was studied with a morphologic type of the Actinomadura genus, Acd. verrucosospora (Nonomura a. Ohara, 1971. Spore formation begins with the division of a hypha by cross-partitions which, as a rule, appear as monolayered on cross-sections, thus differing from sporulation septae found in other actinomycetes. The structure and shape of septae change in the course of spore formation: first, they consist of one layer and have the same thickness as the cell wall; later, they consist of several layers and their thickness is uneven (the shape of dumbbels). In the course of spore maturation, thick regions of the septae are destroyed. Mature spores are characterized by the presence of vacuoles, the thichened cell wall and outer sheath; the latter bears rounded structures arranged in conglomerates which resemble grapes. The process of sporogenesis and the structure of spores in Actinomadura verrucosospora differ from those in other species of the Actinomadura genus (Williams et al., 1974; Soina et al., 1975); therefore, this genus of actinomycetes is heterogenous.