show Abstracthide AbstractMetabolic interactions and genetic exchange are important features of microbial communities. We performed genome-resolved metagenomics to characterize communities performing dissimilatory perchlorate reduction, a metabolism that involves reactive chlorine species and horizontal gene transfer of a conserved functional gene cluster. Distinct communities from source marine sediment and enrichments of varying salinity were recovered, and enriched populations included perchlorate-reducing bacteria as well as putative interacting populations of chlorate-reducing, sulfur-reducing, and fermentative microorganisms. Vectors for perchlorate reduction genes and a novel gene cluster involved in perchlorate reduction were also identified.