CLONING AND MAPPING OF THE GENETIC-DETERMINANTS FOR MICROCIN C51 PRODUCTION AND IMMUNITY

Microcin C51 is a small peptide antibiotic produced by Escherichia col i cells harbouring the 38 kb low copy number plasmid pC51, which codes for microcin production and immunity. The genetic determinants for mi crocin synthesis and immunity were cloned into the vectors pBR325, pUC 19 and pACYC184. Physical and phenotypic analysis of deletion derivati ves and mutant plasmids bearing insertions of transposon Tn5 showed th at a DNA fragment of about 5 kb is required for microcin C51 synthesis and expression of complete immunity to microcin. Partial immunity can be provided by a 2 kb DNA fragment. Mutant plasmids were tested for t heir ability to complement Mic(-) mutations. Results of these experime nts indicate that at least three plasmid genes are required for microc in production. The host OmpR function is also necessary for microcin C 51 synthesis.