Cable Bacteria Accelerate the Anaerobic Removal of Pyrene in Black Odorous River Sediments

Cable bacteria play essential roles in biogeochemical processes in sediments by long-distance electron transport (LDET). A potential relationship has been found between cable bacteria and organic contaminant removal, but the mechanisms remain unclear. In this study, the response of cable bacteria to pyrene was investigated in the sediments with or without pyrene, and the effect of cable bacteria on pyrene removal was explored by connecting or blocking the paths of cable bacteria to the suboxic zones. The results showed that pyrene significantly influenced the microbial community structure and the composition of cable bacteria. The removal efficiencies of pyrene were significantly increased with the enrichment of cable bacteria, while sulfur-reducing microorganisms and aromatic compound degraders were also significantly enriched and correlated with cable bacteria abundance. Metagenomic analysis showed that cable bacteria had a potential LDET-bound acetate/formate respiratory pathway to gain energy. The presence of pyrene probably select and enrich the cable bacteria with high toleration of organic contaminant and change the related functional microbial community, leading to the acceleration of pyrene removal. This study provides new insights into interaction mechanisms between contaminants and cable bacteria, shedding light on the applications of cable bacteria in the bioremediation of contaminants in sediments.