CHARACTERIZATION OF ENTEROBACTERIA STRAIN S PRODUCING BROAD RANGE ANTIBIOTICS MICROCINS

As a result of screening among 11956 enterobacteria strains isolated f rom feces of normal children, grown-ups and lambs, seven active microc in-producing strains were obtained. The microcins were shown to be pep tides or their derivatives with a low molecular weight (less than 10 0 00) and a broad spectrum of activity, mainly against gramnegative bact eria. According to cross immunity criteria the microcins studied belon ged to two different types. Those of type I could be further classifie d into two subtypes on the account of difference in the spectrum of an tibacterial activity. In 5 cases out of 7 the microcin-producing abili ty and immunity to microcins have been attributed to plasmids that the strains harboured. The effect of microcins on sensitive cells depende d on ompR and ompF gene products.