Department of Biological Sciences, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark.
Nature. 2010 Feb 25;463(7284):1071-4. doi: 10.1038/nature08790.
Some bacteria are capable of extracellular electron transfer, thereby enabling them to use electron acceptors and donors without direct cell contact. Beyond the micrometre scale, however, no firm evidence has previously existed that spatially segregated biogeochemical processes can be coupled by electric currents in nature. Here we provide evidence that electric currents running through defaunated sediment couple oxygen consumption at the sediment surface to oxidation of hydrogen sulphide and organic carbon deep within the sediment. Altering the oxygen concentration in the sea water overlying the sediment resulted in a rapid (<1-h) change in the hydrogen sulphide concentration within the sediment more than 12 mm below the oxic zone, a change explicable by transmission of electrons but not by diffusion of molecules. Mass balances indicated that more than 40% of total oxygen consumption in the sediment was driven by electrons conducted from the anoxic zone. A distinct pH peak in the oxic zone could be explained by electrochemical oxygen reduction, but not by any conventional sets of aerobic sediment processes. We suggest that the electric current was conducted by bacterial nanowires combined with pyrite, soluble electron shuttles and outer-membrane cytochromes. Electrical communication between distant chemical and biological processes in nature adds a new dimension to our understanding of biogeochemistry and microbial ecology.
一些细菌能够进行细胞外电子转移，从而使它们能够在不进行直接细胞接触的情况下使用电子受体和供体。然而，在微米尺度之外，以前没有确凿的证据表明在自然界中，空间上分隔的生物地球化学过程可以通过电流耦合。在这里，我们提供的证据表明，通过去纤化沉积物运行的电流将沉积物表面的耗氧作用与沉积物深处的硫化氢和有机碳的氧化作用耦合起来。改变覆盖沉积物的海水中的氧气浓度会导致在有氧区以下 12 毫米处的沉积物中硫化氢浓度迅速（<1 小时）变化，这种变化可以通过电子的传输来解释，而不是通过分子的扩散来解释。质量平衡表明，沉积物中超过 40%的总耗氧量是由从缺氧区传导的电子驱动的。有氧区中明显的 pH 峰值可以用电化学氧还原来解释，但不能用任何常规的有氧沉积物过程来解释。我们认为电流是由细菌纳米线与黄铁矿、可溶性电子穿梭体和外膜细胞色素共同传导的。自然中不同的化学和生物过程之间的电通信为我们理解生物地球化学和微生物生态学增加了一个新的维度。
