醌类化合物-导电矿物联合介导的微生物胞外电子传递及对湿地砷还原的作用机制

Arsenic pollution of soil has attracted wide global attention. Dissimilatory metal reduction bacteria (DRMB) play an important role in the reductive dissolution of metal in soils. Although domestic and foreign investigations have studied the microbial extracellular electron transfer (EET) mediated by quinonoids compounds (QCs), the investigations based on electroconductive minerals (EMs) mediated EET process were severely limited at present. In addition, the understanding on EET process mediated by QCs coupled with EMs and the regarding impacts to the arsenic transformation from flooded soil were even quite limited. In this project, the arsenic-enriched soils were sampled for the microcosm assays to investigate the EET process of DRMB resulting from the coupled mediation by QCs and EMs. Meanwhile, a series of analytical methods, including high-throughput sequencing, fluorogenic quantitative PCR, DNA-stable isotope probing technology and bioelectrochemistry analysis, were employed to study the characteristics of EET process mediated by QCs coupled with EMs. The compositions of arsenic-reducing microbes in soil are analyzed under the molecular level. The coupled relationship between the biotransformation of organic substrate and the reductive dissolution of arsenic and iron are disclosed. Overall, the mechanisms of the EET process mediated by QCs coupled with EMs and the regarding impacts to the arsenic transformation from flooded soil are illuminated. The obtained results will enrich the understanding of mobilization and transformation of arsenic in soils and thereby provide an important theoretical foundation for controlling arsenic pollutions.

土壤的砷污染已引起全世界广泛关注，异化金属还原微生物是驱动土壤金属还原迁移的重要“引擎”。尽管国内外已有研究开展了对醌类化合物介导微生物胞外电子传递的研究，但是对于导电矿物所介导的微生物胞外电子传递认识有限，尤其基于醌类化合物与导电矿物所联合介导的微生物胞外电子传递及对土壤砷转化迁移过程一直没有得到清晰的认识。本项目将以砷污染的湿地土壤为研究对象，以醌类化合物与导电矿物联合介导的微生物胞外电子传递为切入点，结合实验室模拟培养，采取高通量测序、荧光定量PCR、稳定性同位素核酸探针及土壤生物电化学体系等来研究醌类化合物与导电矿物共介导下微生物胞外电子传递的特征；在分子水平上探究土壤中砷还原微生物类群组成及分布；探究土壤颗粒导电性与砷/铁还原及有机碳转化的耦联关系；阐明醌类化合物与导电矿物联合介导的微生物胞外电子传递对湿地砷还原迁移的影响机制，为丰富湿地土壤砷的迁移转化及控制提供重要理论依据。

土壤的砷污染已引起全世界广泛关注，异化金属还原微生物是驱动土壤金属还原迁移的重要“引擎”。腐殖质和导电矿物在土壤中无处不在，而基于醌类物质与导电矿物共介导的异化金属还原微生物胞外电子传递必然左右着土壤中砷/铁的转化迁移，这将是砷循环过程中不可忽视的一个重要环节。围绕该项目，主要取得进展如下：1.阐明了光介导半导体矿物协同异化金属还原微生物胞外传递对土壤砷/铁还原转化的促进机制；2.探究了典型金属模式矿物的导电性与微生物胞外电子传递的相关性；3.解析了土壤惰性有机碳腐殖质中的醌类基团是加速微生物胞外电子传递的关键因素；4.在分子层面上，解析了典型模式矿物与土壤有机碳耦合作用一定程度上提升了土壤金属还原菌群的丰度，并且增加了c-cyts色素的表达量，提升了直接电子传递效应。项目组经过3年的努力，已基本阐明半导体矿物联合土壤有机碳协同微生物胞外电子传递对湿地土壤砷/铁还原转化的促进机制；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10篇文章（7篇中科院一区Top，4篇IF>10.0）。