Sequence-based differentiation of strains in the Streptomyces cyaneus species-group

In an extensive numerical phenetic survey, a number of blue, red and gray spored streptomycete strains were grouped together as Streptomyces cyaneus species-group, a taxon which encompasses strains known to produce antitumor antibiotics, notably anthracyclines. In the present investigation these and related streptomycetes were the subject of morphological and 16S rRNA sequencing studies designed to clarify their taxonomic relationships. It is evident from these results that the Streptomyces cyaneus species-group encompasses misclassified strains and members of several distinct species. However, some of the red-spored strains (e.g. Streptomyces janthinus ISP 5206T, Streptomyces roseoviolaceus ISP 5277T and Streptomyces violatus ISP 5209T) formed a distinct clade. In contrast, most of the blue and gray-spored strains showed much less sequence homology between and with one another and were scattered throughout the 16S rRNA Streptomyces tree. The improved classification of this group of streptomycetes provides an essential basis for establishing their industrial and economical significance..