[Genetic mobility of plasmids of Streptomyces erythraeus]

Grossing of S. erythraeus 4 with S. erythraeus 1 resulted in transfer of genetic elements from strain 4 to strain 1 as evidence by the 20 and 18 kb fragments in the experiments on DNA-DNA hybridization. The presence of the genetic elements in strain 1 was the cause of plasmid pSE 21 mobility. In strain 6, a derivative of S. erythraeus 1 plasmid pSE 21 was accompanied by other extrachromosomal DNAs characterized by high instability. During storage of the strain at a temperature of 4 degrees C for more than 1 or 2 months the number of the plasmid pSE 21 copies decreased. When the strain was stored for longer periods (6 months or more) the plasmid DNA was not detectable even with the DNA-DNA hybridization procedure. The results of hybridization of a fraction of the extrachromosomal DNA of S. erythraeus 6, the Bam HIB fragment of plasmid pSE 21 with the total DNA of strains 1, 4, 5, 6 and BTCC 2 of S. erythraeus and hybridization of DNA of plasmid pSE 21 with the total DNA of S. erythraeus 6 and 1 showed that (1) strains 1, 5 and BTCC 2 had the same hybridization patterns, (2) the other extrachromosomal DNAs present in the fraction were homologous with the Bam HIA fragment of plasmid pSE 21, (3) chromosomes of strains 1, 4, 5, 6 and BTCC 2 of S. erythraeus also contained DNA homologous to the plasmid Bam HIA fragment. It was suggested that plasmid pSE 21 could be used as a basis for constructing the integrative vector for S. erythraeus.