[Organization and gene expression of plasmid ColD-CA23 connected with colicin biosynthesis]

Organization of genes for colicin, immunity and lysis and regulation of their expression in colicinogenic plasmid ColD-CA23 were studied. The polypeptides synthesised in minicells carrying the ColD plasmid, its Tn5 mutants and the recombinant plasmids constructed by cloning the ColD EcoRV fragments on pBR325 were analysed. The position of the colicin gene promotor is established and direction of the gene transcription determined. The immunity gene was shown to be expressed independently of the gene coding for colicin and believed to have its own SOS-independent promotor. Treatment with mitomycin C of the ColD-carrying cells leads to induction of the synthesis both of colicin and of a 10 KD protein responsible for cell killing and lysis. This protein can be detected in a cultural medium under lysis. Plasmid mutations abolishing synthesis of the lysis protein prevent release of colicin. The colicin and lysis genes are arranged in an operon, the lysis gene being situated next to that of colicin. The ColD genetic map is suggested.