金属还原地杆细菌到巴氏甲烷八叠球古菌种间电子直接传导的分子机理

This research addresses the central scientific question of “the new pathways and control mechanisms for microbial material and energy transformation and metabolism in hydrosphere”. Based on the recent discovery that “microbial direct interspecies electron transfer drives global cycling of carbon and sulfur”, the syntrophy between Geobacter metallireducens and Methanosarcina barkeri is employed as a model system. Our hypothesis states that “G. metallireducens utilizes its cell-surface cytochromes and nanowires to transfer electrons directly to the extracellular electron transfer pathway(s) of M. barkeri.” By using an approach that integrates microbiology, molecular biology, biochemistry, electrochemistry and systems biology methods, electron transfer from cell surface cytochromes of G. metallireducens, through Geobacter nanowires, across the cell envelop of M. barkeri and to the cytoplasmic membrane of M. barkeri is systematically investigated. Molecular understanding of direct electron transfer mechanisms from G. metallireducens to M. barkeri will provide new insights into “the new pathways and control mechanisms for microbial material and energy transformation and metabolism in hydrosphere” and advance research on “the new metabolic mechanisms by which microorganisms drive the transformation and global cycling of carbon，nitrogen and sulfur in the basin water ”.

本研究针对“水圈微生物物质与能量转换和代谢的新途径和新调控机制”这一核心科学问题，根据“微生物种间电子直接传导驱动碳和硫地球化学循环”这一新发现，以“金属还原地杆菌-巴氏甲烷八叠球菌互利共生”为模式系统，提出“金属还原地杆菌通过其表面细胞色素和纳米导线将电子直接传导给巴氏甲烷八叠球菌胞外电子传导通道”的假说。采用微生物学、分子生物学、生物化学、电化学和系统生物学手段相结合的方法，通过系统刻画电子由金属还原地杆菌表面的细胞色素、经过纳米导线、穿过巴氏甲烷八叠球菌膜套、最后传导到巴氏甲烷八叠球菌质膜的过程，从分子水平上阐述金属还原地杆菌到巴氏甲烷八叠球菌种间电子直接传导机理，为“水圈微生物物质与能量转换和代谢的新途径及新调控机制”提供新认识，为研究“驱动流域碳氮硫转化与循环的微生物代谢新机制”开辟发展的新动力。

本项目以金属还原地杆菌-巴氏甲烷八叠球菌互营共培养及金属还原地杆菌-硫还原地杆菌互营共培养为模式系统，利用微生物学、分子生物学、生物化学、电化学和系统生物学相结合的方法，系统比对研究了电子由金属还原地杆菌传导到巴氏甲烷八叠球菌和硫还原地杆菌的分子机理。研究结果发现金属还原地杆菌的四个孔蛋白-细胞色素复合体均参与了将电子由周质空间、通过外膜传导到细胞外的过程。在细胞外，金属还原地杆菌的菌毛纳米导线参与了将电子传导给巴氏甲烷八叠球菌和硫还原地杆菌的过程。硫还原地杆菌利用其菌毛和细胞色素纳米导线受金属还原地杆菌传导过来的电子、并将接受的电子传导给细胞外膜上的四个不同的孔蛋白-细胞色素复合体。最后，这些复合体将电子由细胞外、通过外膜传导到细胞内的周质空间。系统揭示了微生物种间电子直接传导的分子过程。为微生物种间电子传导在环境科学、合成生物学及其它生物技术中的应用提供了理论基础。