Long-distance electron transfer by G. sulfurreducens biofilms results in accumulation of reduced c-type cytochromes.
Long-distance electron transfer by G. sulfurreducens biofilms results in accumulation of reduced c-type cytochromes.
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DOI：
10.1002/cssc.201100734
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发表时间：
2012-06
期刊：
影响因子：
8.4
通讯作者：
Bond, Daniel R.
中科院分区：
文献类型：
--
作者：
Liu, Ying;Bond, Daniel R.
Geobacteraceae细菌群具有将细胞质代谢与外表面氧化还原化学联系起来的天然能力。虽然这种能力很可能是利用环境中的金属氧化物作为电子受体而进化出来的，但它偶然地允许从这些细菌中收集电流为了将电子从细胞质转移到外膜以外的受体，成功的金属还原细菌解决了多种生物物理挑战。细胞内氧化反应产生的电子被插入细胞质膜，然后在细胞壁和外膜上传递100多个电子，氧化还原蛋白随后必须与一系列不可预测的金属氧化物相互作用。除了在细胞分裂后形成多细胞群落的子细胞之间传递电子或访问高度不规则的表面外，还需要在尺度上延伸许多微米的长距离电连接。[3-6]细胞间和通过Geobacter生物膜的电子转移的概念模型差异很大。一些数据表明，电子通过具有金属样导电性的蛋白质纤维传播，而其他证据支持一个模型，涉及沿蛋白质和多糖支架组织的细胞色素之间的电子交换。[8,9]这些模型都是建立在现象观察的基础上的，即电子在生物膜中移动了几十微米，但它们都缺乏生物膜内蛋白质状态的数据，这可能会限制关键事件的发生。光谱法在电位分析中的应用为直接测量电极还原细菌中多种辅因子的氧化还原状态提供了一种新的工具。[10-13]最近的两项研究专门研究了能够在维持生理条件的情况下监测硫还原Geobacter sulfreducens生物膜中c型细胞色素还原状态的光谱电化学反应器的构建，而另一项研究则关注细胞-电极界面。在这些情况下，完全生长的生物膜是这些非侵入性测量的主要目标。生物膜厚度对电子向c型细胞色素转移动力学的影响还没有比较或根据最近的电子转移模型进行处理。
The Geobacteraceae group of bacteria possesses a natural ability to link cytoplasmic metabolism with redox chemistry at their external surface. Although this capability likely evolved to take advantage of environmental metal oxides as electron acceptors,[1] it fortuitously allows collection of electrical current from these bacteria.[2] To transfer electrons from the cytoplasm to acceptors beyond the external membrane, successful metalreducing bacteria solve multiple biophysical challenges. Electrons produced by oxidative intracellular reactions are inserted into the cytoplasmic membrane and then transferred over 100 across the cell wall and outer membrane, where redox proteins must then interact with an unpredictable array of metal oxides. In addition to relaying electrons between daughter cells after cell division that grow as multicellular communities or access highly irregular surfaces, there is a need for longer-distance electrical connections that extend many microns in scale.[3–6]Conceptual models of electron transfer between cells and through Geobacter biofilms vary widely. Some data suggests that electrons travel via protein fibers with metallic-like conductivity,[7] whereas other evidence supports a model involving exchange of electrons between cytochromes organized along protein and polysaccharide scaffolds.[8, 9] Each of these models are built upon the phenomenological observation that electrons travel tens of microns through a biofilm, but both lack data on the status of proteins within the biofilm, which could place constraints on key events. The use of spectroscopic methods during potentiometric analysis has provided a new tool to directly measure the redox status of multiple cofactors in electrode-reducing bacteria.[10–13] Two recent studies specifically addressed construction of spectroelectrochemical reactors able to monitor reduction states of c-type cytochromes in Geobacter sulfurreducens (G. sulfurreducens) biofilms while maintaining physiological conditions, whereas another focused on the cell–electrode interface. In these cases, fully grown biofilms were the primary target of these noninvasive measurements. The effect of biofilm thickness on the kinetics of electron transfer to c-type cytochromes has not been compared or addressed in light of recent electron-transfer models.
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