Wang, X.; Wang, H.; Qian, X.; Wei, H.; Zhong, Y.; Xiu, Z.; Yu, L.; Wang, S.; Zhang, H.; Yan, H.; Sun, W.; Yang, Y.

Hexachlorobutadiene (HCBD), a persistent organic pollutant (POP), poses a significant threat to ecological environments and human health. While anaerobic microbial transformation is a promising remediation strategy, the specific microorganisms and metabolic mechanisms involved have remained poorly understood. This study demonstrates the successful enrichment of an anaerobic microbial consortium from river sediment, with lactate as an electron donor, capable of transforming HCBD. Within 240 days, 62.5 mol of HCBD was sequentially dechlorinated through pentachlorobutadiene (PCBD), tetrachlorobutadiene (TeCBD), trichlorobutadiene (TCBD), and dichlorobutadiene (DCBD) to chlorobutadiene (CBD). Co-amendment with HCBD and trichloroethene (TCE) resulted in complete removal of both compounds. 16S rRNA gene sequencing and quantitative PCR showed enrichment of Dehalococcoides, linking its population growth to HCBD and TCE dechlorination. This study demonstrates that Dehalococcoides growth was associated with HCBD transformation in the enrichment cultures, broadens our understanding of the metabolic capabilities of Dehalococcoides, and identifies a candidate gene for this important environmental process, offering valuable insights for the bioremediation of sites contaminated with HCBD.