Microbial dechlorination of historically present and freshly spiked chlorinated dioxins and diversity of dioxin-dechlorinating populations

Microbial activity changes from methanogenic to nonmethanogenic during dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and aged tri- and monoCDD congeners. The peri-dechlorination pathway of 2,3,7,8-substituted hepta- to pentaCDDs produces 2,3,7,8-tetraCDD. Another dechlorination pathway is the peri- lateral pathway of non-2,3,7,8-substituted congeners. Peri and triCDD dechlorination occur due to the activity of nonmethanogenic, non-spore-forming microbial subpopulations. Both freshly spiked and aged PCDDs undergo microbial reductive dechlorination.