Ribostamycin production by a mutant of butirosin producing bacteria.

By the use of our improved colony selection technique, xylostasin and ribostamycin producing mutants were isolated from nitrosoguanidine treated Bacillus circulans B15M, a producer of butirosins A and B. Among these structurally related aminoglycosides, ribostamycin is the well-known product of a Steptomyces and has not been isolated as a bacterial metabolite. A selected mutant of strain 306, which produces xylostasin and ribostamycin, was futher mutagenized in expectation of getting an improved strain having the ability to accumulate a large amount of ribostamycin in the culture broth. One mutant, strain 451, derived from strain 306, produced ribostamycin free of xylostasin.