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Metal ions contamination may inhibit microorganisms involved in the biodegradation of organic compounds and affect biodegradation rates. Therefore, it is likely that bioremediation of xenobiotics-contaminated soils and waste will require inoculation with efficient biodegrading microbial communities, with capabilities of being resistant to heavy metals as well. Two different transconjugants (Pseudomonas sp. KM12TC and P. ueruginosu TC) were constructed by conjugation experiments. Results on MTC, induction and growth inhibition strongly indicated that arsenic-resistant plasmid, pKM20, could be mobilized, and the newly acquired phenotype of pKM20 was not only expressed but also well regulated, resulting in newly acquired resistances to As^(5+), As^(3+), and Sb^(3+) in addition to Cd^(2+), Zn^(2+) and Hg^(2+). The phenol-degradation efficiencies of Pseudomonus sp. KM 12TC were maintained significantly even at high heavy metal concentrations at which these efficiencies of P. ueruginosu TC were completely impaired. The results in this study on the effect\ of heavy metals on phenol degradation, especially after conjugation, are the first ever reported. All the results described in this study encourage to establish a goal of making "designer biocatalysts" which could degrade certain xenobiotics in the area contaminated with multiple heavy metals.
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