Plasmid DNA in the erythromycin producing microorganism, Streptomyces erythreus NRRL 2338.

Streptomyces erythreus NRRL 2338, the erythromycin producing microorganism, contains extrachromosomal (plasmid) DNA. Four different plasmids, pSE1, pSE2, pSE4 and pSE6 present in the wild-type strain have characteristic mobilities on agarose gel electrophoresis, molecular weight and restriction endonuclease digestion patterns. Treatment of the wild-type strain with ethidium bromide or acridine orange gave two variants, one that could not convert erythronolide B to 3 (alpha)-mycarosylerythronolide B and another than produced 2 approximately 3 times more erythromycin A than the parental strain.