New anthracycline glycosides from Micromonospora. I. Description of the producing strain

During the course of successive mutagenic treatments of Streptomyces peucetius var. caesius, producer of anthracyclines, a novel mutant was isolated from a plate of the surviving population. This mutant showed remarkable morphological, cultural and biochemical differences when compared to the original strain. The new culture produced four new glycosides of a novel class within the group of the daunorubicin related anthracyclines, two of which were also present in the original strain. To our surprise the taxonomical study carried out on this mutant allowed its assignment to the genus Micromonospora ORSKOVA (1923). The possibilities of whether this new strain has originated from a contamination or from a mutation are discussed. The type strain is Micromonospora sp. strain B211 F.I. (identical to ATCC 31366; DSM 1190; FRI 4363).