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Electric Currents in Sediment and Soil

Final Report Summary - COULOMBUS (Electric Currents in Sediment and Soil)

Living in the sea bottom is no easy. Oxygen only penetrates the top millimeter or so and most of the food is buried deeper down. Animals have learned to circulate oxygen and use siphons, while microbes either make do with a poor anaerobic life or reside at the surface, waiting for the dissolution and upwards diffusion of food molecules left over from the anaerobes. In 2010 the existence of another solution was reported – electric currents – and the aim of COULOMBUS was to investigate this surprise discovery. Respiration is essentially the transfer of electrons from food to oxygen, but how can organisms administrate this over centimeters distance as reported? The answer found was a hitherto unknown form of life which was named cable bacteria. These centimeters long bacteria with thousands of cells take up electrons from food at one end and conduct them through internal wires to oxygen at the other end. From being beyond our imagination they have now been reported in aquatic environments from hot and cold seeps in ocean deeps to coastal waters, beaches, salt marshes, and mangroves and further up in estuaries, streams, lakes, and even aquifers. Many species have been identified and by wiring up the sediments with up to 10,000 kilometers of “cables” per square meter they take control of energy and element cycling including transformations of oxygen, carbon, sulfur, nutrients and minerals. As result of the electric currents they also create measureable electric fields which further influence ion fluxes. The internal electric wires of cable bacteria severely resisted the scientific investigation efforts, but recently putative conductive elements in a grid of strong strings have been identified - perhaps the foundation for future electronics?