[Phenotypic expression of plasmid pPL7065 in Bacillus pumilus in free and integrated states]

There are about 20 copies of pPL7065 plasmid in cells of Bacillus pumilus ATCC7065 with molecular weight of 4.7 X 10(6) daltons. A spontaneous purine dependent mutant LK1 was isolated which contained no autonomous plasmid. However, the presence of the plasmid in LK1 cells was proved by DNA - DNA hybridization. To accomplish this, hybrid plasmid p1G1 was constructed by cloning pPL7065 on a vector pBR322 and multiplying it in Escherichia coli C600. The plasmid then was hybridized with chromosomal DNA of Bac. pumilus LK1. A pur+ revertant has been obtained from LK1 containing autonomous plasmid pPL7065, similar to the parental strain ATCC7065. These results are indicative of pPL7065 integrated into the chromosome of LK1. Bacteria having the autonomous plasmid are oligosporogeneous and produce specific antibiotics. Integration of the plasmid into bacteria causes pur phenotype, normal sporulation and a change in antibiotic synthesis and resistance. LK3 strain which lost pPL7065, sporulates normally and produces the antibiotic that inhibits growth of Bac. pumilus ATCC7065.