Exploring reaction mechanisms of dissimilatory ferric reduction-coupled sulfur oxidation (DIRSO) by acidophilic prokaryotes and its relevance for bioleaching and acid mine drainage formation

生物浸出过程和酸性矿山废水（AMD）的产生主要是由微生物的好氧铁和硫氧化驱动的，它们也受到微生物异化铁还原耦合硫氧化（DIRSO）的影响很大，DIRSO已被描述为厌氧以及好氧条件下在非常低的pH值。此外，缺乏知识存在DIRSO相关的铁和硫的形态转化，微生物群落结构和功能，铁和硫代谢途径的分子机制，在嗜酸菌，特别是在嗜热嗜酸菌。拟开展的研究项目旨在通过嗜热嗜酸古菌和中嗜酸细菌探索DIRSO的生理和（生物）化学。微生物矿物与不同的含铁矿物和不同的硫化合物的相互作用将通过明确的实验室实验与纯培养物，包括新的分离物，定义的混合培养物以及微生物群落从酸性环境中进行研究。高端分析技术，如同步辐射技术（XANES，SR-XRD，STXM），在线拉曼光谱，HPLC等，将被应用于识别和量化中间，不稳定的化学化合物参与的Fe-S耦合氧化还原反应在溶液中和矿物表面。通过检测硫化合物中间体，我们将能够描述DIRSO在所描述的和新的内消旋和热嗜酸菌中的反应途径。同时，我们将探索浸出过程中微生物群落结构和功能演替，并通过转录组学和比较蛋白质组学阐明嗜热嗜酸菌的铁/硫代谢途径。在应用方面，DIRSO将通过改变pH值、电子供体（还原硫化合物）和不同的三价铁矿物在好氧-厌氧耦合系统中进行研究，以研究反应动力学，从而改善生物浸出并更好地预测AMD的产生。

Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by microbial aerobic iron and sulfur oxidation, and they are also greatly influenced by microbial dissimilatory iron reduction coupled to sulfur oxidation (DIRSO) which has been described for anaerobic as well as aerobic conditions at very low pH. Studies in DIRSO by acidophiles are rare, and these focused on mesophilic acidophiles but hardly on thermophilic acidophiles. Moreover, a lack of knowledge exists for DIRSO-related iron and sulfur speciation transformation, microbial community structure and function and the molecular mechanism of iron and sulfur metabolic pathways in acidophiles, especially in thermoacidphiles. The proposed research project aims to explore the physiology and (bio)chemistry of DIRSO by thermoacidophilic archaea and mesoacidophilic bacteria. Microbe mineral interactions with different ferric iron containing minerals and different sulfur compounds will be studied by well-defined laboratory experiments with pure cultures including novel isolates, defined mixed cultures as well as microbial communities from acidic environments. High-end analytic techniques such as synchrotron radiation-based techniques (XANES, SR-XRD, STXM), online Raman spectroscopy, HPLC among others, will be applied to identify and quantify intermediary, labile chemical compounds involved in the Fe-S-coupled redox reactions in solution and on mineral surfaces. By detecting the sulfur-compound intermediates we will be able to describe reaction pathways of DIRSO in described and novel meso- and thermoacidophiles. At the same time, we will explore the microbial community structure and functional succession during leaching process and elucidate the iron/sulfur metabolic pathways of thermophilic acidophiles by transcriptomics and comparative proteomics. Towards application, DIRSO will be investigated in aerobic-anaerobic coupling systems by varying pH, electron donor (reduced sulfur compounds) and different ferric iron minerals for studying reaction kinetics in order to improve bioleaching and to better predict AMD generation.