[Integrative suppression of antibiotic formation in Bacillus pumilus]

Relationship between antibiotic production and pPL 7065 plasmid integration into the chromosome of B. pumilus ATCC 7065-K was studied. With this purpose hybridization of plasmid DNA isolated from strain ATCC 7065 producing no antibiotic was performed with chromosome DNA of B. pumilus ATCC 7065 and W20, as well as B. subtilis and E. coli K-12. Plasmid DNA labeled with 3H was used in the experiments. It was found to be slightly bound with DNA of B. subtilis (0.8 per cent), E. coli K-12 (0.2 per cent), and B. pumilus W20 (3 per cent). Still, its hybridization with chromosome DNA of B. pumilus ATCC 7065-K was effective (11 per cent). It is concluded to be due to hybridization between plasmid pPL 7065 of strain ATCC 7065 and the same plasmid but integrated into the chromosome of the antibiotic-producing strain ATCC 7065-K. Therefore, derepression of the antibiotic biosynthesis is a sequence of integrative suppression.