[Microcins: their nature and genetic determination].

A number of gram-negative bacteria are capable of synthesizing the low molecular mass antibiotics microcins, the substances with molecular masses up to 10 000 D possessing a broad range of antibiotic activity. The synthesis is not lethal for the producing cells and is not induced by DNA-damaging agents. The investigated microcins are either of oligopeptide nature or are analogues of methionine. Five types of microcins have been described. The A- and C-types of microcins inhibit protein synthesis, microcins B suppress DNA replication, microcins D and F affect cellular energy potential. Microcin synthesis and immunity to microcins are shown to be plasmid mediated. The role of microcins in ecology of enterobacteria and the ranking among bacterial antibiotics are discussed.