Microbially-mediated halogenation and dehalogenation cycling of organohalides in the ocean

Microbially mediated organohalide cycling in the ocean has profound implications for global element cycles and climate, but the phylogeny, coding potential, and distribution of the halogenation-dehalogenation cycling microorganisms remain unknown. Here, we construct an organohalide-cycling database (HaloCycDB) to explore the global atlas of halogenation-dehalogenation cycling genes and microorganisms in the ocean from 1,473 marine metagenomes. FlaHase and HyDase/RDase as predominant halogenase- and dehalogenase-encoding genes account for 80.24% of all potential organohalide-cycling activities. We identify 80.91% RDase and 91.35% RDase-containing prokaryotes as unknown organohalide-cycling genes and microorganisms, respectively, which greatly expand the diversity of dehalogenation phylogeny and coding potential. Further integration of microbial cultivation with protein structure prediction and molecular docking elucidates 4 unique "microorganism-enzyme-organohalide" patterns for organohalide dehalogenation in the ocean. Our results provide the first insight into microbial halogenation-dehalogenation cycling of organohalides and associated yet-to-be-explored resources in the ocean.