纳米催化材料增强希瓦氏菌双向胞外电子传递的途径及分子机理研究

In microbial electrochemical systems, the applications of nano-catalytic materials can greatly enhance the extracellular electron transfer (EET) abilities of electroactive microorganisms in general. However, their significant enhancements can not be fully explained by using the existing EET model, because the current EET model is usually proposed based on the studies of conventional electrode materials and thereby the substantial effect of electrode’s electrocatalytic activity on microbial EET process is often overlooked. In order to better understand the scientific issue of “the interaction mechanism of interfacial electron transfer between nano-catalytic materials and electroactive microorganisms”, a project based on nanostructured molybdenum carbides (nano-Mo2C) with highly electrocatalytic activity and a model electroactive microorganism (Shewanella oneidensis MR-1) is proposed. Firstly, the regularity effect of nano-Mo2C on Shewanella bidirectional EET ability and the relative parameters will be investigated to clarify structure-function relationship. Subsequently, for the sake of analyzing the main regulatory pathway and model about the Shewanella EET process, the effect of nano-Mo2C on the composition and structure of Shewanella biofilm grown on an electrode and the gene transcription levels will be studied by means of electrochemical analysis, biochemical analysis, in-situ micrometry and comparative transcriptome techniques. The electrocatalytic behaviors of nano-Mo2C towards different EET carriers including flavins, cytochrome proteins and other possible candidates will be studied carefully, then the key catalytic and regulatory targets that are responsible for the increased EET ability of Shewanella strain on the nano-Mo2C interface will be screened and identified followed by the elaboration of their molecular mechanism. This project is expected to illuminate the synergetic mechanism from biological and electrochemical catalyses in microbial electrode.

在微生物电化学体系中，纳米催化材料可显著增强微生物胞外电子传递（EET）能力。基于传统电极所建立的现有EET模型，未考虑电极电催化活性对微生物EET的影响，用来解释纳米催化材料的增强作用存在一定局限性。为了深入理解“纳米催化材料与微生物间界面电子传递互作机制”科学问题，本项目拟以高电催化活性的纳米碳化钼（Mo2C）和模式电活性微生物（希瓦氏菌）为研究对象，在考察纳米Mo2C对希瓦氏菌双向EET过程参数的影响规律基础上，综合运用电化学分析、生化分析、原位微测技术、比较转录组学等手段，分析纳米Mo2C催化界面对希瓦氏菌电极生物膜组成与结构、基因转录水平的影响，探究纳米Mo2C调控希瓦氏菌EET过程的主要途径和作用模型；通过研究纳米Mo2C对不同EET媒介体（膜色素蛋白、核黄素等）的电催化行为，确定关键催化靶点及分子机理，以期从“影响规律—调控途径—关键靶点”多方面阐述生物与电化学协同催化机制。

为了深入理解“纳米催化材料与微生物间界面电子传递互作机制”这一科学问题，本项目以高催化活性的纳米碳化钼（Mo2C）和硫化亚铁（FeS）为对象，综合运用纳米技术、电化学、生物化学和转录组学等方法，探究了纳米Mo2C修饰电极界面对模式电活性微生物Shewanella oneidensis MR-1双向EET过程（即阳极产电和阴极富马酸还原）的影响规律及主要调控途径，研究了FeS/Shewanella杂化膜中FeS纳米界面增强细菌EET的机制。结果表明，纳米Mo2C修饰的碳毡阳极显著增强了S. oneidensis MR-1产电（即向外EET能力），单室电解池中恒电位（+0.2 V vs SCE）放电电流密度为1.5 A m-2（提高了9.4倍），双室微生物燃料电池中最大输出功率密度为212 W m-2（提高了7.8倍）；纳米Mo2C修饰的碳布阴极显著增强了电驱动的S. oneidensis MR-1富马酸还原（即向内EET能力），在-0.36 V（vs SHE）电极电势下电流消耗密度为0.041 mA cm-2（提高了4.1倍）。通过对比野生株与Mtr途径色素蛋白缺失株，发现Mtr途径是S. oneidensis MR-1双向EET跨内外膜的主要通道；而纳米Mo2C功能化修饰界面岁内源性电子介体核黄素存在的催化行为，使得后者的氧化还原反应动力学更为快速，是增强细菌与电极界面间电子交换的关键所在。比较转录组学分析发现，纳米Mo2C界面对S. oneidensis MR-1能量代谢和信号传导相关基因表达存在调控作用。在原位合成的FeS/Shewanella杂化膜中，纳米FeS可充当固相电子介体，与S. oneidensis MR-1的Mtr途径交互从而实现协同增强效应，显著增强了EET速率。本项目以“影响规律-调控途径-关键靶点”主线，阐明了纳米催化材料增强希瓦氏菌双向EET的途径及机制，为微生物电化学系统中生物与电化学协同催化理论提供了重要支撑。