Pock forming plasmids from antibiotic-producing Streptomyces.

Abstract

Pock forming ability of 15 plasmids isolated from antibiotic-producing Streptomyces was examined with polyethylene glycol mediated protoplast transformation. Four plasmids (pSF765, pSF689, pSF674 and pSF601) have pock forming ability on S. lividans 66. Each putative transformants isolated from the center of pock regions harbored plasmids with the same restriction enzyme cleavage sites as original plasmids. The plasmids from the transformants produced pock, which were morphologically identical to the original plasmids. Transformation frequency of S. lividans 66 with pSF689 from S.lividans 66 was at least 500-fold higher (5 .times. 105 transformants/.mu.g DNA) than that with the plasmid isolated from the original strain (103 transformants/.mu.g DNA). In case of pSF765 the transformation frequency was not changed (about 105 transformants/.mu.g DNA) by replications in S. lividans 66. Expanded restriction enzyme maps for the 4 plasmids are reported.