[Variability of the levorin producer, Actinomyces levoris Krass].

: Natural variation of the levorin-producing organism Act. levoris, strain 28 was studied with respect to the colony morphology and production of levorin and levoristatin. The population of strain 28 consisted of 3 morphological colony types, the main type amounting to 99.7 percent. The strain variation with respect to production of levorin and levoristatin ranged from 20 to 180 and from 0 to 300 percent respectively as compared to the control. Mutant M-28 differing from the initial strain by the colony morphology, moderate phage titer and preferable production of levoristatin was isolated as a result of repeated passages of strain 28 onto agarized Chapek media with starch without maintaining selection. Variants differing from the population of strains 28 and M-28 by the ratio of levorin and levoristatin in the culture fluid were selected. No correlation in production of the above antibiotics by strain 28 was noted. Preparations obtained with strain M-28 differed from those obtained with strain 28 in a significant content of levoristatin.