Dehalobacter Dechlorinates Dichloroanilines and Contributes to the Natural Attenuation of Dichloronitrobenzenes at a Complex Industrial Site

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 the northeast of Brazil. Anaerobic biotransformation of these chlorinated compounds was observed in microcosms simulating site conditions, particularly when an electron donor was added. To disentangle specific transformation reactions, subcultures 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 the dechlorination of DCAs. These findings helped attribute function to the microbial community data retrieved from field samples to improve the conceptual site model and enable the 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.