Long-distance electron transport by cable bacteria in mangrove sediments

Cable bacteria are long, filamentous sulphur-oxidizing bacteria that induce long-distance electron transport in aquatic sediments. They turn the seafloor into an electro-active environment, characterized by currents and electrical fields, and when present, they exert a strong impact on the geochemical cycling in the seafloor. However, cable bacteria have only recently been discovered, and so their geographical distribution and habitat distribution remain largely unknown. Here we report field evidence that cable bacteria are present and active in mangrove sediments. Combining microsensor profiling and fluorescence in situ hybridization, we recorded high filament densities (77 m cm(-2)) and the signature of electrogenic sulphur oxidation in sediments of grey mangroves near Melbourne, Australia. Our findings suggest that cable bacteria could be a keystone microbial species in the geochemical cycling of mangroves.