[Effect of protoplast formation on the antibiotic activity of the Streptomyces fradiae 165 strain--a producer of tylosin].

Streptomyces is characterized by genetic instability evident from high frequency of changes in various properties of secondary metabolites occurring spontaneously or under the influence of certain factors. Protoplast formation is one of such factors. The paper is concerned with the influence of protoplast formation and subsequent regeneration into the mycelial form on antibiotic potency of S. fradiae strain 165. It was shown that protoplast formation led to changes in antibiotic potency of separate colonies and shifts in the potency in the direction of its increasing. The antibiotic potency of certain variants after protoplast formation was 2 to 2.5 times higher than the initial one. Changes due to protoplast formation of S. fradiae strain 165 were not stable and lost after 4-5 passages on agar media. Comparative restriction analysis of total DNA of the variants with different potency levels did not provide detection of changes in the genome of the strains isolated after protoplast formation.