Carbofuran degradation mediated by three related plasmid systems

Two carbofuran-metabolizing Sphingomonas strains, TA and CD, were isolated from soils with differing histories of exposure to carbofuran. These strain s were compared with a previously described strain, Sphingomonas sp. CFO6, with regard to growth rate, formation of metabolites, and plasmid content a nd structure. Extensive regions of similarity were observed between the thr ee different plasmid systems as evidenced by cross hybridization. In additi on, all three systems harbor IS1412,;an insertion sequence (IS) element inv olved in heat-induced loss of carbofuran phenotype in CFO6, and heat-induce d carbofuran deficient mutants of all three strains correlated with loss of IS1412. A carbofuran deficient mutant of TA generated by induction of IS e lements was complemented by reintroduction of the wild-type plasmid, confir ming the presence of genes required for carbofuran metabolism on this plasm id. Carbofuran metabolism in these three strains is clearly linked via plas mids of different numbers and sizes that share extensive common regions, an d carbofuran-degrading genes may be associated with active IS elements. (C) 2000 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.