Water content as a primary parameter to determine microbial reductive dechlorination activity in soil. Water content as a primary parameter to determine microbial reductive dechlorination activity in soil

Organohalide-respiring bacteria (OHRB) employ reductive dehalogenases to catalyze halogen removal from a variety of organohalides, which could be utilized for in situ remediation of different contaminated sites, e.g., groundwater, sediment and soil. In this study, we investigated the impact of water content (0-100%), soil type (laterite, brown soil and black soil) and inoculated OHRB (Dehalococcoides mccartyi CG1 and a river sediment culture) on reductive dehalogenation of perchloroethene (PCE) and polychlorinated biphenyls (PCBs) and associated microbial communities. Results suggested water content as a rate-limiting parameter in governing dechlorination activities in soil but not in sediment and water, possibly through mediation of cell-to-organohalide mobility of OHRB. By contrast, interestingly, organohalide-dechlorinating microbial communities were predominantly clustered based on soil type, rather than water content and inoculated OHRB. This study provides knowledge on the impact of major parameters on OHRB-mediated reductive dechlorination in groundwater, sediment and soil for future optimization of in situ bioremediation of organohalides.