微生物电网驱动河流异质性沉积物中长距离氮硫元素循环机制

Element cycles in river sediments are driven by “biogeobattery”, which predominantly comprises of electrochemically active microorganisms (EAM). Important though, little is known about how EAM drive element cycles in heterogenous microcosms of river sediments. Recently, our team had identified several filamentous electrochemically active microorganisms (F-EAM), including electrogenic and electroconductive ones from the river heterogenous sediments in Pearl River Delta. Inspired from that, we hypothesize that there is a comprehensive microbial power network (MPN) driving the distant nitrogen and sulfur cycles in river sediment, which contains backbone MPN (B-MPN) with F-EAM being the scaffold, and the spatially separated and heterogenous local MPNs (L-MPN). The former is where F-EAM channel the terminal sulfide oxidation to the terminal nitrate reduction by conducting long-distance electron transport, and the latter is where actual redox reactions occur, creating the pairwise anode and cathode. This project will investigate the structure and function of MPN in typical redox river sediments of Pearl River Delta, elucidate the synergistic interactions of B- and L-MPN on regulating distant nitrogen and sulfur cycles, illuminate the inducing mechanisms of electrogenic and electroconductive F-EAM in channeling the separated redox pairs in distant nitrate reduction and sulfide oxidation as well as the key factors involved, and finally to establish the mathematical model that outlines how MPN drives this process. Achievements from this very research will be sure to lay a constructive foundation for future explorations on geochemical element cycles in the hydrosphere.

河流沉积物元素循环依靠以电化学活性微生物(EAM)为重要组成的“生物地电池”驱动，但目前对于该“生物地电池”异质性微环境间的EAM驱动机制了解极少。申请者在珠三角河流异质性沉积物中发现多种长线状电化学活性微生物(F-EAM)，包括产电型和导电型F-EAM。据此提出“微生物电网(MPN)驱动长距离氮硫循环”假说，即由以F-EAM为骨架的骨干电网(B-MPN)和具有空间异质性的局域电网(L-MPN)共同组成的MPN驱动长距离氮硫元素循环。课题将系统分析珠三角典型氧化还原电位差异质性沉积物中MPN结构功能，探讨B-MPN与L-MPN互作特点及对长距离氮硫元素循环的协同调控作用，阐明产电型与导电型F-EAM介导空间隔离硝酸还原硫氧化过程的作用机制及关键影响因素，建立MPN驱动长距离氮硫元素循环的数学模型。课题所产生的知识与技术对于研究EAM在其它水圈环境中驱动地球元素循环的作用机理亦有借鉴作用。

河流沉积物元素循环依靠以电活性微生物为重要组成的微生物电子传递网络驱动。研究阐明沉积物异质性微环境中微生物电子传递网络结构功能及其调控机制具有重要意义。本项目以珠三角典型河流沉积物为主要研究对象，在建立微生物电子传递网络研究方法体系、建成全球首个电微生物资源信息库及功能分析预测网站的基础上，取得了多项新发现：. 1）河流沉积物中电活性微生物独特的分布特点：长线状电缆细菌（e-Cable）呈现明显的生物地理分布特征，其丰度沿沉积物深度递减；网状结构的赖氨酸芽胞杆菌（e-Net）的丰度随深度递增；典型短杆状电活性微生物地杆菌（e-Dot）的丰度与沉积物深度没有显著相关性。. 2）微生物导电网络新模式：赖氨酸芽胞杆菌GY32在产电过程中细胞逐渐伸长，最长可超过1mm，并相互连接成具有良好导电特性的网络；该网络中细胞是绝缘的，而细胞周身合成的蛋白纳米线具有明显的导电性，整合了已知的地杆菌产生胞外纳米导线和电缆细菌产胞内纳米导线两种革兰氏阴性菌的导电特点。. 3）以电缆细菌为核心驱动的电动氧扩散机制：上覆水溶解氧浓度的升高可显著提高电缆细菌的丰度和产电硫氧化活性，进而促进硫代谢、有机质降解等功能微生物的富集，形成紧密的互利共生网络，其中硫酸盐还原菌通过硫酸盐呼吸耦合复杂有机质降解，有效促进深层沉积物中顽固性有机物的降解转化。. 4）长线状电活性菌赖氨酸芽胞杆菌与电缆细菌之间的协同互作机制：赖氨酸芽胞杆菌可通过形成导电网络而降低沉积物的扩散阻力，促进沉积物中的硫酸根向上覆水迁移，从而缓解电缆细菌产电硫氧化过程所引起的硫酸盐累积问题。. 项目共发表论文39篇，包括Nat. Commun.等第一标注的SCI论文33篇；申请国内外专利13件，其中美国专利1件、PCT专利4件、获授权中国发明专利8件；并与国际电微生物学领军机构丹麦电微生物卓越中心共同建设了“中国-丹麦电微生物国际联合研究中心”。