Endogenous biohydrogen from a rhizobium-legume association drives microbial biodegradation of polychlorinated biphenyl in contaminated soil

•PCB77 biodegradation efficiency increased significantly in soils treated with endogenous H2.•Endogenous H2 selected bacteria harboring PCB degradation genes.•Different taxa conducting successive metabolic steps of PCB metabolism.•Enriched hydrogenotrophic taxa encoding biphenyl oxidation genes drove PCB biodegradation through endogenous H2.