Research on the biocathode-based bioelectrochemical system (BES) has attracted extensive attention because of its ability to increase the electricity-driven production of high-value fuels or chemicals by relying on microbial cells as catalysts. An extracellular electron transfer (EET) that makes electrical connections to microorganisms plays a key role in the BES. Compared with the better understanding of the EET-to-anode connection, the understanding of the mechanism and elements involved in inward EET from cathodes to microbes remains limited. Additionally, the low capability of the EET limits its applications in BESs for producing chemicals. Here, we introduced the Mtr pathway into Escherichia coli cells by expressing ccmABCDEFGH from E. coli and mtrABC from Shewanella oneidensis. Through selection by electrochemical pressure, the evolved E. coli could use electricity to increase the production of succinate in direct BES and enhance the electroactivity. In addition, in studying the mechanism of inward EET, menaquinone was found to be one of the key components of inward EET, and it is essential for the fumarate reduction reaction. Lastly, the intracellular NADH and ATP levels showed that there were differences in the energy conservation coupling between the electron transfer routes of the inward Mtr pathway and the electron mediator.

中文翻译：

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在大肠杆菌中使用向内的Mtr途径从阴极直接吸收电子。

基于生物阴极的生物电化学系统（BES）的研究已引起广泛关注，因为它有能力依靠微生物细胞作为催化剂来提高电力驱动的高价值燃料或化学物质的生产。与微生物形成电连接的细胞外电子转移（EET）在BES中起着关键作用。与更好地了解EET到阳极的连接相比，对从阴极到微生物的内向EET涉及的机理和元素的了解仍然有限。另外，EET的低能力限制了其在用于生产化学品的BES中的应用。在这里，我们通过表达来自大肠杆菌的ccmABCDEFGH和来自沙瓦氏菌的mtrABC来将Mtr途径引入大肠杆菌细胞。通过电化学压力的选择，生成了E。大肠杆菌可以利用电来增加直接BES中琥珀酸的产生并增强电活性。此外，在研究内向EET的机理时，发现甲萘醌是内向EET的关键成分之一，对富马酸酯的还原反应至关重要。最后，细胞内NADH和ATP水平表明，内向Mtr途径的电子转移途径与电子介体之间的能量守恒耦合存在差异。