纳米材料介导的微生物胞外电子传递及对湿地土壤金属还原的作用机制

Arsenic/chromium pollution has attracted wide attention in the world. Although the biotic and abiotic processes described above may all play a role in arsenic/chromium reduction, it has been concluded that microorganisms play the defining role in catalysing the redox transformations that ultimately control the transformation of arsenic/chromium . The problem of arsenic release is particularly acute in the Delta region od south Asia. Previous research of outside and our group had confirmed that nanomaterials can promote extracellular electron transfer and had a significant effect on reduction of arsenic/chromium. Due to the complexity of environmental media and environmental conditions, the role of arsenic/chromium transformation- the extracellular electron transfer process has not a clear understanding. In present project, we propose to elucidate extracellular electron transfer associated with nanao-conductive materials and arsenic/chromium reduction in anaerobic soil. So the project is intended to collect arsenic/chromium contamination samples from typical subtropical anaerobic soil in Fujian Province and combined with laboratory simulation and pure culture experiments. The use of micro-structural analysis, electrochemical analysis combined high-throughput sequencing technology and real-time PCR to determine extracellular electron transfer mode via nano-conductive mineral; to analyze possibility of extracellular long distance electron transfer and its impact on arsenic/chromium reduction process; to research microbial community composition and distribution of anaerobic soils at the molecular level under nanoaprticles condition; to confirm the conductivity and coupling relationship with arsenic/chromium reduction process; to clarify extracellular electron transfer process and the reduction of arsenic/chromium in the anaerobic soils via nano-conductive materials. This research is expected to provide new insights into the mechanisms of extracellular electron transfer associated with nano-conductive minerals and represents an important first step in developing the capacity to predictively model the contributions and response of arsenic/chromium reduction process.

金属砷/铬污染已引起国内外的广泛关注，微生物异化还原导致湿地土壤砷/铬转化是个重要的生物地球化学过程，国内外已有的研究工作和本课题组的前期工作已经证实纳米材料具有促进胞外电子传递且对砷/铬的还原有着显著影响，但由于环境介质和环境条件的复杂性，纳米材料介导的微生物胞外电子传递与金属转化一直没有得到清晰的认识。本项目拟以实验室纯培养、室内模拟及原位采集我国典型亚热带湿地土壤砷/铬污染样品为研究对象，利用微结构分析、生物电化学分析联合高通量测序及荧光定量PCR 等现代生物技术，探究纳米材料介导下微生物胞外电子传递模式；分析其胞外电子及对砷/铬转化过程的影响；在分子水平上研究纳米材料介导下湿地土壤主要微生物的种类及分布、纳米材料导电性及与砷/铬还原过程的耦联关系；阐明纳米材料介导下湿地土壤微生物胞外电子传递过程及对湿地土壤金属转化的影响机制，为湿地土壤金属的迁移转化过程与控制提供理论依据。

纳米材料介导的微生物异化还原导致湿地土壤砷/铬转化是个重要的生物地球化学过程。本项目探究了导电碳纳米材料和金属矿物纳米材料介导下微生物胞外电子传递模式；分析了胞外电子及对砷/铬转化过程的影响；在分子水平上研究纳米材料介导下湿地土壤主要微生物的种类及分布、纳米材料导电性及与砷/铬还原过程的耦联关系；阐明纳米材料介导下湿地土壤微生物胞外电子传递过程及对湿地土壤金属转化的影响机制，取得主要进展如下：.1、阐明了纳米材料关键特征及介导微生物胞外电子传递的作用机制。.系统分析典型纳米材料及其特征在微生物胞外电子传递过程中的贡献，发现纳米材料的生物相容性、导电性、醌类基团等是促进胞外电子传递的关键特征。通过微结构分析发现纳米材料不仅能负载在微生物细胞表面，而且还能够进入细胞里面共同作用促进电子传递效率。证实纳米材料通过应激微生物产生黄素或促进细胞色素C蛋白表达来促进胞外电子传递过程。.2、明确了导电碳纳米材料在微生物胞外电子传递耦联铬还原过程中作用机制。.从纳米材料介导胞外电子传递的关键特征出发，合成了生物相容性好、导电性强、具有醌类基团、方便回收的GO/PVA膜。研究发现其能显著促进S. xiamenensis的Cr(VI)过程，而且能通过循环使用提高GO/PVA-S. xiamenensis的生物催化性。并进一步阐明了GO/PVA膜介导S. xiamenensis还原Cr(VI)作用机制：通过由细胞外膜到内逐渐分阶段提升c-Cyts基因的表达水平从而提高Cr(VI)的还原效率。.3、建立了典型纳米材料介导下污染土壤微生物组成、电子传递与砷/铬转化的关系。.项目组探讨了纳米材料介导微生物胞外电子传递与土壤砷/铁/铬转化的关系，发现纳米材料能够与土壤砷/铁形成复合体，而且纳米材料能增大对土壤DOM的生物利用度及改变功能微生物种群的丰度，促进了微生物的胞外电子传递过程并影响土壤金属的转化。纳米材料表面所含有的醌类结构及导电性是影响微生物胞外电子传递与土壤砷/铁形态转化关系的重要原因。.项目组经过四年的努力，已基本阐明微生物胞外电子传递与纳米材料之间的关系及其对湿地土壤砷/铬转化的影响机制；项目设置的研究内容已执行并实现了研究目标。项目负责人在国内外期刊以通讯作者或共同通讯作者发表SCI收录文章18篇文章（其中JCR 1区7篇，5篇影响因子大于6，ESI高被引论文1篇）。