ABSTRACTThe Oil Refinery (OR) consortium is a model methanogenic enrichment culture for studying anaerobic benzene degradation. Over 80% of the culture’s bacterial community is comprised of two closely related strains of benzene-fermentingDesulfobacterota(designated ORM2a and ORM2b) whose mechanism of benzene degradation is unknown. Two new metagenomes, including a fully closed metagenome-assembled genome (MAG) for ORM2a, enabled a thorough investigation of this culture’s proteome. Among the proteins identified were Bam-like subunits of an ATP-independent benzoyl-CoA degradation pathway and associated downstream beta-oxidation proteins producing acetyl-CoA. The most abundant proteins identified mapped to two ORM2 gene clusters of unknown function. Syntenic gene clusters were identified in one other known benzene degrader,Pelotomaculumcandidate BPL, as well as a handful of contigs assembled from hydrothermal vent metagenomes. Extensive searches against reference sequence and structural databases indicate that the first (“Magic”) gene cluster likely catalyzes the chemically difficult benzene activation step. The second (“Nanopod”) gene cluster is predicted to code for an efflux system that pumps excess benzene out of cells, mitigating some of its toxigenic effects. Phylogenomic analyses place ORM2a and ORM2b within a novel genus of benzene-degrading specialists which we propose naming “CandidatusBenzenivorax”. We hope to engage the research community to help in confirming the roles of the proteins in the “Magic” and “Nanopod” gene clusters, and to search through their own cultures for these features.