Dehalobacter dechlorinates dichloroanilines and contributes to the natural attenuation of dichloronitrobenzenes at a complex industrial site

Abstract

The potential for bioremediation of dichloroanilines (2,3- and 3,4-DCA) and dichloronitrobenzenes (3,4-, 2,5- and 2,3-DCNB) was investigated using inocula from an industrial site in northeast of Brazil. Anaerobic biotransformation of these chlorinated compounds was observed in microcosms simulating site conditions, particularly when electron donor was added. To disentangle specific transformation reactions, sub-cultures from active anaerobic microcosms were enriched with individual DCA or DCNB isomers. In these single-compound enrichment cultures, DCNB isomers were reduced to the corresponding DCA. Each DCA isomer was stoichiometrically dechlorinated to the corresponding monochloroaniline (CA) isomers. Further dechlorination of CA to aniline was noted. The reduction of DCNB to DCA was sustained by known fermenters and possibly Desulfitobacterium, while Dehalobacter was clearly responsible for dechlorination of DCAs. These findings helped to attribute function to microbial community data retrieved from field samples to inform the conceptual site model and enable identification of bioactive zones and rate-limiting conditions at a complex site. More generally, these data broaden the understanding of the metabolic repertoire of Dehalobacter and provide a model for incorporating microbial community data into site remediation efforts. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/638192v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1667948org.highwire.dtl.DTLVardef@a4a128org.highwire.dtl.DTLVardef@507067org.highwire.dtl.DTLVardef@103a155_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Short synopsis statementA diverse microbial community contributes to natural attenuation at a complex contaminated site. Notably, dichloroanilines produced by biologically-mediated nitroreduction of dichloronitrobenzenes were dechlorinated by Dehalobacter.