1] Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark [2] Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
ISME J. 2014 Jun;8(6):1314-22. doi: 10.1038/ismej.2013.239. Epub 2014 Jan 23.
Filamentous Desulfobulbaceae have been reported to conduct electrons over centimetre-long distances, thereby coupling oxygen reduction at the surface of marine sediment to sulphide oxidation in sub-surface layers. To understand how these 'cable bacteria' establish and sustain electric conductivity, we followed a population for 53 days after exposing sulphidic sediment with initially no detectable filaments to oxygen. After 10 days, cable bacteria and electric currents were established throughout the top 15 mm of the sediment, and after 21 days the filament density peaked with a total length of 2 km cm(-2). Cells elongated and divided at all depths with doubling times over the first 10 days of <20 h. Active, oriented movement must have occurred to explain the separation of O2 and H2S by 15 mm. Filament diameters varied from 0.4-1.7 μm, with a general increase over time and depth, and yet they shared 16S rRNA sequence identity of >98%. Comparison of the increase in biovolume and electric current density suggested high cellular growth efficiency. While the vertical expansion of filaments continued over time and reached 30 mm, the electric current density and biomass declined after 13 and 21 days, respectively. This might reflect a breakdown of short filaments as their solid sulphide sources became depleted in the top layers of the anoxic zone. In conclusion, cable bacteria combine rapid and efficient growth with oriented movement to establish and exploit the spatially separated half-reactions of sulphide oxidation and oxygen consumption.
丝状脱硫杆菌科已被报道能够在数厘米长的距离上传导电子，从而将海洋沉积物表面的氧气还原与亚表层的硫化物氧化耦合起来。为了了解这些“电缆细菌”是如何建立和维持电导率的，我们在将原本没有可检测丝状菌的硫化沉积物暴露于氧气中 53 天后，对一个种群进行了跟踪。10 天后，整个沉积物的前 15 毫米都建立了电缆细菌和电流，21 天后，丝状菌密度达到峰值，总长度为 2 公里厘米(-2)。在最初的 10 天内，细胞在所有深度上伸长和分裂，倍增时间小于 20 小时。为了解释 O2 和 H2S 之间的分离，必须发生活性、定向运动。丝状体直径从 0.4-1.7 μm 不等，随着时间和深度的增加而普遍增加，但它们的 16S rRNA 序列同一性大于 98%。生物量和电流密度的增加比较表明细胞生长效率很高。虽然丝状体的垂直扩展随着时间的推移持续进行，并达到 30 毫米，但电流密度和生物量分别在 13 天和 21 天后下降。这可能反映了由于缺氧区顶层中固体硫化物源的枯竭，短丝状体的破裂。总之，电缆细菌将快速有效的生长与定向运动结合起来，建立并利用硫化物氧化和氧气消耗的空间分离的半反应。
