Microbially mediated organohalide cycling in ocean have profound implications for global element cycles and climate, but the phylogeny, coding potential and distribution of the halogenation-dehalogenation cycling microorganisms remain unknown. To explore the global-scale microbially-mediated halogenation and dehalogenation cycling of organohalides in ocean, we first developed an organohalide-cycling gene database (HaloCycDB) to support organohalide-cycling metagenomics analyses; then, we collected 1,473 metagenomes from 506 oceanic sites to reveal geographic distribution of organohalide-cycling microorganisms and functional genes at the global scale; the microorganisms and genes for halogenation and dehalogenation cycling of organohalides were further catalogued to explore novel taxonomic and genetic resources; last, the ‘microorganism-enzyme-organohalide’ patterns for reductive dehalogenation were analyzed and confirmed with protein structure prediction, molecular docking and laboratory cultivation experiments. To the best of our knowledge, this study provides the first insight into the halogenation and dehalogenation cycling of organohalides in ocean, which provides a roadmap for exploring marine organohalide-associated bioresources. 

organohalide cycling