The phylogenetic structure of the genus Streptosporangium

The phylogenetic structure of the genus Streptosporangium was determined by comparative 16S rDNA sequence analysis of 26 Streptosporangium strains, including the type strains of all validly-described Streptosporangium species. Streptosporangium forms a phylogenetically coherent genus and appears to be most closely related to members of the genus Streptomyces. Ten of the thirteen type strains investigated were shown to be highly related, forming strain cluster I, with a substructure of five lineages. This cluster includes the type strain of the type species of the genus, S. roseum DSM 43021(T). Strain cluster II is composed of the other three type strains, i.e., S. corrugatum DSM 43316(T), S. claviforme DSM 44127(T) and S. viridialbum DSM 43181(T). Five non-type strains of validly described Streptosporangium species were also investigated; four of these were highly related to their respective type strains, while the other was more closely related to the type strain of another species. Of seven non-validly described taxa studied, four were highly related to S. roseum DSM 43021(T), belonging to strain cluster I, one forms a potential sixth subcluster of cluster I, one belongs to cluster II, and S. ''sibiricum'' fell outside the radiation of Streptosporangium. Characteristic patterns of signature oligonucleotides differentiate members of Streptosporangium from members of Streptomyces, cluster I organisms from those of cluster II, and the strains of the different subclusters of cluster I from each other. These signatures could be used for future design of specific oligonucleotide probes or primers.