PSEUDOMONAS-PUTIDA STRAINS WHICH CONSTITUTIVELY OVEREXPRESS MERCURY RESISTANCE FOR BIODETOXIFICATION OF ORGANOMERCURIAL POLLUTANTS

Improved biocatalysts for mercury (Hg) remediation were generated by r andom mutagenesis of Pseudomonas putida with a minitransposon containi ng merTPAB, the structural genes specifying organomercury resistance. Subsequent selection for derivatives exhibiting elevated resistance le vels to phenylmercury allowed the isolation of strains that constituti vely express merTPAB at high levels, conferring the ability to cleave Hg from an organic moiety and reduce the freed Hg(II) to the less toxi c elemental form, Hg0, at greater rates. Constitutive overexpression o f merTPAB had no apparent effect on culture growth rates, even when Hg (II) was initially present at otherwise toxic concentrations. These pr operties were also combined with benzene and toluene catabolism, allow ing detoxification of the metal component of phenyl mercuric acetate, as well as degradation of its aromatic moiety.