基于AFM-SECM技术原位研究希瓦氏菌单细胞的胞外电子传递机制

The essence of microbial extracellular electron transfer (EET) process is the redox reaction associated with electron transfer pathways, which plays an important role in energy conversion and elemental geochemistry cycle. At present, the analysis of EET pathways is developing fast from macroscopic biofilm to in situ, visual and microcosmic aspects, which was promoted by advanced electrochemical and nanoprobe technology. However, the electrical conductivity and indirect electron transfer capability of single-cell were restricted to determine in situ conditions, because a single microbial cell is not easy to grow adhering to the wall in solution. This project intends to achieve microbial cells adhere steadily and independently onto an ITO electrode in oxygen-free electrolyte with a constant potential applying on the electrode. Besides, conductive atomic force microscope will be used to identify the morphology and the electrical conductivity of a single cell in situ conditions. Moreover, the ability of indirect electron transfer of single cell will be quantified by precisely controlling the distance between a nanoprobe and the cell, with atomic force microscope and scanning electrochemical microscope. This study will reveal the electron transfer mechanisms of microbial metabolism between the cells and their outside environment from physical chemistry perspective, and impel the application of EET mechanisms in the fields of bioenergy, microbial synthesis and environment remediation.

微生物的胞外电子传递（EET）过程本质上是与电子转移相关的氧化还原反应，在物质能量转化和元素的地球化学循环过程中起重要作用。先进的电化学技术和纳米探针技术正促进EET机制向原位、直观、微观的方向快速发展，但是，溶液中的单个微生物细胞难以附着在电极界面，限制了其导电性和间接电子传递能力的原位电化学测定，致使EET机制目前尚不完善且存在争议。本项目拟采用恒电位厌氧培养技术，实现希瓦氏菌以单细胞分散的形式持久附着在电极界面；利用导电原子力显微镜的纳米探针电极现场原位测定单细胞的导电性；结合原子力显微镜和扫描电化学显微镜的优势，从单细胞层面定量微生物的间接电子传递能力。本研究将从物理化学角度揭示微生物代谢过程中与外界环境之间的电子传输机制，从而推动微生物的EET在生物能源利用、纳米材料合成和环境污染修复等领域的应用。

微生物的氧化还原过程在元素的生物地球化学循环与物质能量转化过程中发挥着关键作用。本项目基于扫描电化学显微镜（SECM）、原子力显微镜（AFM）和AFM-SECM，从宏观的生物膜层面逐渐过渡至从微观的单细胞层面研究希瓦氏菌的氧化还原性质，直观、有效地测定了单细胞和生物膜在形貌和电子传递途径方面的区别和联系；从物理化学角度揭示了微生物代谢过程中与外界环境之间的电子传输机制，发现乳酸代谢的直接电子传递途径基于外膜细胞色素c蛋白对间接电子传递途径的促进作用；促进了研究生物/非生物界面的物质能量转化技术向原位、直观、微观的方向发展，推动微生物胞外电子传递在生物能源利用、纳米材料合成和环境污染修复等领域的应用。