Genetic Evidence for a Plasmid Controlling Fertility in an Industrial Strain of Streptomyces rimosus

Summary: A plasmid (SRP1) determines most of the genetic recombination which occurs between marked derivatives of our strain of Streptomyces rimosus. SRP1− strains occur with a frequency of about 0.3% amongst spores of SRP1 + strains. In SRP1 +xSRP1 − crosses, SRP1 is transferred to more than 50% of the SRP1 − parent. SRP1 +xSRP1 − crosses are about 100 times more fertile than SRP1+xSRP1+ crosses (10−3 to 10−4 compared with 10−5 to 10−7). A very low frequency (about 10−8) of true recombinants occurs in the absence of SRP1.