The mutant 113 was obtained from a natural non-antibiotic producing Streptomyces sp. 1254 by UV irradiation. It produced a group of novel anthracycline compounds designated mutactimycins. Strain 1254 was placed in the genus Streptomyces on the basis of its morphological characteristics and chemical properties of cells. According to Williams's numerical taxonomical data based on more than 50 physiological tests of a total of 375 type strains, the strain 1254 is considered to be more resemble to S. omiyaensis in the cluster of S. exfoliatus. The whole cell hydrolysate of mutant 113 contains DL-DAP, arabinose, galactose and rhamnose, but its cell envelope does not contain mycolic acids. Comparing with all genera of cell chemotype IV without mycolic acids and with Sacchrothrix which contains taxonomically significant rhamnose, mutant 113 shows differences with them respectively on FA composition or MK and PL patterns. The conclusion we can draw now is that mutant 113 doesn't belong to the same genus Streptomyces as its parent strain 1254 does, and is more close to the genus Sacchrothris.