Self-Constructed Electrically Conductive Bacterial Networks
Self-Constructed Electrically Conductive Bacterial Networks
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DOI：
10.1002/anie.200804750
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发表时间：
2009-01-01
影响因子：
16.6
通讯作者：
Hashimoto, Kazuhito
中科院分区：
文献类型：
--
作者：
Nakamura, Ryuhei;Kai, Fumiyoshi;Hashimoto, Kazuhito
微生物在矿物表面的附着是自然环境中引发广泛的生物化学和地质事件的基本过程。[1]希瓦氏菌属[2]由异化金属还原菌组成，通常在地下沉积物中发现，具有识别氧化铁表面的能力[3]，并启动细胞外电子转移（ET）[4-8]到附着的氧化铁作为其代谢的最终过程。这是一个重要的过程，因为它影响铁的生物地球化学循环，[9]并且它不仅因为微生物代谢策略的新方面而受到关注[5-8]，而且还因为它在微生物燃料电池中的适用性而受到关注。[10]外膜（OM）氧化还原蛋白，C型十血红素细胞色素（c-Cyt），在介导ET从细胞到铁（III）氧化物中起着至关重要的作用。[4-7大量的研究集中在纯化的OM蛋白的电化学和光谱研究上。[11]然而，通过直接监测完整细胞的ET过程进行的研究很少，因此该过程的机制在很大程度上仍然没有解决。本文报道了S. loihica PV-4在氧化铁（III）存在下自组装成导电网络，并证明了纳米矿物在促进细菌网络中的长距离细胞外ET过程中的作用。探讨完整S. loihica PV-4，我们使用单室三电极系统，乳酸盐作为碳源和电子供体。使用表面积为1.8cm2的光学透明导电玻璃、掺杂锡的In 2 O3（ITO）电极作为工作电极，并将其放置在反应器的底表面上。将细胞加入反应器后立即产生电流（图1a），并达到0.4-0.6 μA的恒定值。电流产生是从细胞到电极的电连接的结果，随后是电子从OM c-Cyt注入到ITO电极，这通过无细胞上清液中不存在氧化还原物质来表明。此外，在0.1-4.0的OD 600范围内，电流基本上不依赖于600 nm处的光学细胞密度OD（图1a，插图）。这一结果表明，目前的一代从S。Loihica由直接附着到电极表面的细胞主导。换句话说，单个细胞与其他细胞电绝缘，因此长距离ET过程即使存在，也比c-Cyt介导的ET到电极表面的效率低得多。
Microbial attachment to mineral surfaces is a fundamental process for initiating a broad range of biochemical and geological events in a natural environment.[1] The genus Shewanella,[2] which consists of dissimilatory metal-reducing bacteria often found in subsurface sediments, has the ability to recognize the surface of iron (III) oxides [3] and initiate extracellular electron transfer (ET)[4–8] to the attached iron oxides as a terminal process in its metabolism. This is an important process for its influence on the biogeochemical cycling of iron,[9] and it has also gained attention not only for a new aspect of the metabolic strategy of microorganisms,[5–8] but also for its applicability in microbial fuel cells.[10] The outer-membrane (OM) redox proteins, c-type decaheme cytochromes (c-Cyt), play a crucial role in mediating ET from the cell to iron (III) oxides.[4–7, 11] A great deal of research has been focused on the electrochemical and spectroscopic investigation of the purified OM proteins.[11] However, few studies have been performed by directly monitoring the ET process of intact cells, and therefore the mechanism of this process has largely remained unsolved. Herein, we report the ability of S. loihica PV-4 to selfassemble into an electrically conductive network in the presence of iron (III) oxides, and demonstrate the role of semiconductive nanominerals in promoting a long-distance extracellular ET process in the bacterial network. To probe the extracellular ET of intact cells of S. loihica PV-4, we used a single-chamber, three-electrode system, with lactate as a carbon source and an electron donor. An optically transparent conductive-glass, tin-doped In2O3 (ITO) electrode, with a surface area of 1.8 cm2, was used as the working electrode, and placed on the bottom surface of the reactor. A current was generated immediately after adding the cells into the reactor (Figure 1a), and reached a constant value 0.4–0.6 μA. Current generation is a consequence of electrical connections from the cells to the electrode, followed by the injection of electrons from the OM c-Cyts to the ITO electrode, which is suggested by the absence of redox species in the cell-free supernatant solution. In addition, the current showed essentially no dependence on the optical cell density OD at 600 nm over the OD600 range of 0.1–4.0 (Figure 1a, inset). This result implies that the current generation from S. loihica is dominated by the cells attached directly to the electrode surface. In other words, individual cells are electrically insulated from the others, and thus the long-distance ET process, even if it is present, is much less efficient than the c-Cyt-mediated ET to the electrode surface.