A new antitumor antibiotic, chromoxymycin. I. Taxonomic studies on the producing strain: a new subspecies of the genus Streptomyces.

A new subspecies of the genus Streptomyces, for which the name S. libani subsp. rubropurpureus subsp. nov. is proposed, is described. Soil isolate, strain No. 6362, produces a new antitumor substance chromoxymycin. The strain has a gray or red spore mass color, spiral spore chains with smooth spores, is nonchromogenic, and utilizes most carbon sources. Strain No. 6362 is most closely related to S. libani, although there are differences in colorization of reverse colony and spore chain morphology between each other. Those differences are not enough to establish a new species. It is suitable to consider that strain No. 6362 is identified as a new subspecies in the species of S. libani.