Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, Arizona 85287, USA.
Environ Sci Technol. 2013 May 7;47(9):4934-40. doi: 10.1021/es400321c. Epub 2013 Apr 18.
Thermincola ferriacetica is a recently isolated thermophilic, dissimilatory Fe(III)-reducing, Gram-positive bacterium with capability to generate electrical current via anode respiration. Our goals were to determine the maximum rates of anode respiration by T. ferriacetica and to perform a detailed microscopic and electrochemical characterization of the biofilm anode. T. ferriacetica DSM 14005 was grown at 60 °C on graphite-rod anodes poised at -0.06 V (vs) SHE in duplicate microbial electrolysis cells (MECs). The cultures grew rapidly until they achieved a sustained current density of 7-8 A m(-2) with only 10 mM bicarbonate buffer and an average Coulombic Efficiency (CE) of 93%. Cyclic voltammetry performed at maximum current density revealed a Nernst-Monod response with a half saturation potential (EKA) of -0.127 V (vs) SHE. Confocal microscopy images revealed a thick layer of actively respiring cells of T. ferriacetica (38 μm), which is the first documentation for a gram positive anode respiring bacterium (ARB). Scanning electron microscopy showed a well-developed biofilm with a very dense network of extracellular appendages similar to Geobacter biofilms. The high current densities, a thick biofilm (38 μm) with multiple layers of active cells, and Nernst-Monod behavior support extracellular electron transfer (EET) through a solid conductive matrix - the first such observation for Gram-positive bacteria. Operating with a controlled anode potential enabled us to grow T. ferriacetica that can use a solid conductive matrix resulting in high current densities that are promising for MXC applications.
耐热铁还原菌是一种最近分离得到的嗜热、异化型 Fe(III)还原、革兰氏阳性细菌，具有通过阳极呼吸产生电流的能力。我们的目标是确定耐热铁还原菌的阳极呼吸最大速率，并对生物膜阳极进行详细的微观和电化学表征。耐热铁还原菌 DSM 14005 在 60°C 下，在石墨棒阳极上生长，阳极电位为 -0.06 V（相对于 SHE），在重复微生物电解池（MEC）中进行培养。培养物生长迅速，直到它们达到 7-8 A m(-2)的稳定电流密度，仅使用 10 mM 碳酸氢盐缓冲液，平均库仑效率（CE）为 93%。在最大电流密度下进行的循环伏安法显示出 Nernst-Monod 响应，半饱和电位（EKA）为 -0.127 V（相对于 SHE）。共焦显微镜图像显示出一层厚厚的耐热铁还原菌（38 μm）活跃呼吸细胞层，这是首次记录革兰氏阳性阳极呼吸菌（ARB）。扫描电子显微镜显示出一个发达的生物膜，具有非常密集的细胞外附属物网络，类似于 Geobacter 生物膜。高电流密度、厚生物膜（38 μm）和多层活性细胞，以及 Nernst-Monod 行为支持通过固体导电基质进行细胞外电子转移（EET），这是革兰氏阳性菌的首次观察。通过控制阳极电位进行操作，使我们能够培养耐热铁还原菌，它可以利用固体导电基质，产生高电流密度，这对于 MXC 应用很有前景。
