Long-distance electron transport occurs globally in marine sediments

Abstract

Abstract. Recently, long filamentous bacteria have been reported conducting electrons over centimetre distances in marine sediments. These so-called cable bacteria perform an electrogenic form of sulfur oxidation, whereby long-distance electron transport links sulfide oxidation in deeper sediment horizons to oxygen reduction in the upper millimetres of the sediment. Electrogenic sulfur oxidation exerts a strong impact on the local sediment biogeochemistry, but it is currently unknown how prevalent the process is within the seafloor. Here we provide a state-of-the-art assessment of its global distribution by combining new field observations with previous reports from the literature. This synthesis demonstrates that electrogenic sulfur oxidation, and hence microbial long-distance electron transport, is a widespread phenomenon in the present-day seafloor. The process is found in coastal sediments within different climate zones (off the Netherlands, Greenland, the USA, Australia) and thrives on a range of different coastal habitats (estuaries, salt marshes, mangroves, coastal hypoxic basins, intertidal flats). The combination of a widespread occurrence and a strong local geochemical imprint suggests that electrogenic sulfur oxidation could be an important, and hitherto overlooked, component of the marine cycle of carbon, sulfur and other elements.

Phototrophic marine benthic microbiomes: the ecophysiology of these biological entities

“…This discovery has changed our view on sediment biogeochemistry. Cable bacteria have been found globally in a variety of different benthic environments characterized by moderate to high sulfide concentrations (Burdorf et al ., ). Cable bacteria belonging to the family Desulfobulbaceae transport electrons in marine and freshwater sediments over distances as long as 10 mm and more (Pfeffer et al ., ) (Fig.…”

Transient bottom water oxygenation creates a niche for cable bacteria in long‐term anoxic sediments of the Eastern Gotland Basin

“…The high pore water concentrations of H 2 S and the absence of bioturbation are characteristic features of marine sediments exposed to anoxic bottom waters. Upon bottom water re‐oxygenation, such sediments appear to offer a particularly suitable habitat for cable bacteria (Burdorf et al ., ). For example, high densities and activity of cable bacteria are consistently found in Lake Grevelingen, a seasonally hypoxic coastal water body in the Netherlands, after the re‐appearance of O 2 in the bottom water in fall (Seitaj et al ., ).…”

“…Cable bacteria have now been reported from an increasing number of sites (Burdorf et al ., ). These observations are largely derived from indirect observations, such as ex situ sediment enrichments or from 16S rRNA sequence databases.…”

Application of the isotope pairing technique in sediments: Use, challenges, and new directions

“…In addition to Beggiatoa , succession of other microbes that influence the biogeochemistry of the surrounding sediment may alter N cycling. The recently described cable bacteria have been found in a large number of locations worldwide (Burdorf et al ). These organisms form chains to bridge spatially separated electron donor (sulfide) and acceptor (oxygen or NO 3 − ) (Nielsen et al ; Pfeffer et al ; Marzocchi et al ) and thereby transfer electrons over centimeter distances in sediments.…”