Reductive dehalogenation in marine and estuarine sediments and by sulfate-reducing bacteria.

摘要

The focus of this work has been to study the reductive dehalogenation of various halogenated organics by anaerobic bacteria from marine and estuarine sediments. Sulfate-reducing bacteria in and around the burrows of Saccoglossus sp., marine hemichordates that produce brominated aromatic compounds, will dehalogenate lindane to a mixture of monochlorobenzene and benzene. Work with Desulfovibrio gigas has shown that the presence of a metal sulfide with metallic conductive properties (i.e. FeS, NiS or CoS) is required for dehalogenation to occur. ZnS and MnS, which are described as semiconductive, do not support dehalogenating activity. Cytochrome c3 (Mr 13,000) was purified by gel filtration and ion exchange chromatography from D. gigas. This protein will catalyze the dehalogenation of lindane in the presence of FeS. The fate of 2,4-dichlorophenoxyacetic acid (2,4-D) in four different marine and estuarine sediments was examined. Two sediments had a history of contamination with petroleum products and pesticides while the remaining two did not. Side-chain removal and dehalogenation were only observed in sediments with a history of contamination. The addition of exogenous carbon and electron donors (hydrogen and acetate) stimulated the rate of 2,4-D transformation to 4-chlorophenol. Sulfate, which has previously been shown to completely inhibit reductive dehalogenation in non-marine systems, did not have the same effect in this study. The rate of 2,4-D transformation was slower in the presence of sulfate however, both dehalogenation and sulfate reduction were shown to occur concurrently and both could be stimulated by the addition of hydrogen and acetate. The isolation and characterization of Desulfovibrio sp. strain TBP-1 from an estuarine system in the NY/NJ harbor is described. This organism can grow via halorespiration using brominated phenols and cannot grow in the absence of NaCl. It will effectively dehalogenate brominated phenols it but will not dehalogenate chlorinated, fluorinated or iodinated phenols or halogenated benzoates.