CHEMICAL TRANSFORMATION OF TOXIC METALS BY A PSEUDOMONAS STRAIN FROM A TOXIC-WASTE SITE

Pseudomonas maltophilia strain O-2, isolated from soil at a toxic wast e site in Oak Ridge, Tennessee, catalyzed the transformation and preci pitation of numerous toxic metal cations and oxy-anions. When a viable inoculum (1%) of O-2 was introduced into nutrient broth containing Hg (II), Cr(VI), Se(IV), Pb(II), Au(III), Cd(II), Te(IV), or Ag(I), effec tive removal of the toxic metal was complete within 1, 1, 2, 2,2,4, 5, and 7 d, respectively. The NADPH-dependent reduction of Hg(II) to Hg0 was catalyzed by an inducible mercuric reductase. The reduction of se lenite and tellurite to their insoluble elemental forms appeared to be mediated by an intracellular glutathione reductase that utilized the spontaneously formed bis(glutathio)Se(II) or bis(glutathio)Te(II), res pectively, as pseudosubstrates. The three-electron reduction of hexava lent chromium was catalyzed by a membrane-bound chromate reductase. Th e enzymatic basis for the remaining metal transformations was not imme diately apparent. It is anticipated that Pseudomonas maltophilia and r elated organisms could eventually be exploited for the removal of toxi c metal wastes from selected, heavily polluted sites.