Temporal distributions of functional microbes and putative genes associated with halogenated phenol anaerobic dehalogenation and further mineralization

Growth interactions of functional dehalogenators, degraders and genes (cprAandbamB) during anaerobic mineralization of HACs in an enriched consortium.

Functional Heterologous Production of Reductive Dehalogenases from Desulfitobacterium hafniense Strains

ABSTRACTThe anaerobic dehalogenation of organohalides is catalyzed by the reductive dehalogenase (RdhA) enzymes produced in phylogenetically diverse bacteria. These enzymes contain a cobamide cofactor at the active site and two iron-sulfur clusters. In this study, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-positiveDesulfitobacterium hafniensestrain Y51 was produced in a catalytically active form in the nondechlorinating, cobamide-producing bacteriumShimwellia blattae(ATCC 33430), a Gram-negative gammaproteobacterium. The formation of recombinant catalytically active PceA enzyme was significantly enhanced when its dedicated PceT chaperone was coproduced and when 5,6-dimethylbenzimidazole and hydroxocobalamin were added to theS. blattaecultures. The experiments were extended toD. hafnienseDCB-2, a reductively dehalogenating bacterium harboring multiplerdhAgenes. To elucidate the substrate spectrum of therdhA3gene product of this organism, the recombinant enzyme was tested for the conversion of different dichlorophenols (DCP) in crude extracts of an RdhA3-producingS. blattaestrain. 3,5-DCP, 2,3-DCP, and 2,4-DCP, but not 2,6-DCP and 3,4-DCP, were reductively dechlorinated by the recombinant RdhA3. In addition, this enzyme dechlorinated PCE to trichloroethene at low rates.

Anaerobic Dehalogenation of Hydroxylated Polychlorinated Biphenyls by Desulfitobacterium dehalogenans

ABSTRACT Ten years after reports on the existence of anaerobic dehalogenation of polychlorinated biphenyls (PCBs) in sediment slurries, we report here on the rapid reductive dehalogenation ofpara-hydroxylated PCBs (HO-PCBs), the excreted main metabolites of PCB in mammals, which can exhibit estrogenic and antiestrogenic activities in humans. The anaerobic bacteriumDesulfitobacterium dehalogenans completely dehalogenates all flanking chlorines (chlorines in ortho position to thepara-hydroxyl group) from congeners such as 3,3′,5,5′-tetrachloro-4,4′-dihydroxybiphenyl.