Isolation and Characterization of Plasmid pUOl Mediating Dehalogenation of Haloacetate and Mercury Resistance in Moraxella sp. B

Plasmid pUO1 which specifies haloacetate dehalogenase H-1 and H-2 and mercuric reductase was isolated from a fluoroacetate-assimilating Moraxella strain B. From the spontaneous mutant deficient in H-2 enzyme derived from strain B, plasmid pUO11 specifying H-1 enzyme and mercuric reductase was also isolated. The molecular sizes of pUO1 and pUO11 were estimated to be 43.7 ± 1.6 Mdal and 40.1 ± 1.3 Mdal, respectively, by electron microscopy. These values were in good agreement with those estimated by electrophoretic analyses of the cccDNA and its restriction endonuclease digests. The digestion patterns of both plasmid DNAs were analogous, suggesting that plasmid pUO11 was the deletion mutant derived from pUO1. It could be presumed that the deleted DNA segment had a molecular size of about 3.6 Mdal.