微生物膜胞外电子传递强化多环芳烃高效降解的作用机制

Soil pollution by aromatic hydrocarbon (PAH) is increasing worldwide and poses a great threat to human health. Biodegradation is one of the most potential and efficient remediation methods. The microbial biofilm is found to have the ability to degrade polycyclic aromatic hydrocarbons (PAHs) with high efficiency, however, the degradation process and mechanism are still unclear. Microbial extracellular electron transfer is an important driving force for environmental biochemical processes such as degradation of organic pollutants. Therefore, it is helpful to understand the mechanism of PAHs degradation by microbial biofilm by exploring the coupling process and mutual effect between extracellular electron transfer and PAHs degradation. Thus, in this project, the extracellular electron transfer properties and the biodegradation kinetics of PAHs by two PAHs degrader, Micrococcus sp. PHE3 and Mycobacterium sp. NJS-P bacteria, will be studied. Firstly, the morphological and structural characteristics of degrader biofilms will be monitored timely by methods of environmental scanning electron microscopy and infrared spectroscopy. Then, biochemical and electrochemical experiments will be conducted to explore the redox activities of degrader biofilm and extracellular polymeric substances (EPS), with the purpose of revealing the electron transfer characteristics of biofilms. Through carefully monitoring the PAHs degradation kinetics, we expect to build the relationship curve between extracellular electron transfer and PAHs degradation processes, with the purpose of revealing their coupling relationships and mutual effects. The expression of functional proteins in extracellular polymeric substance will be analyzed by proteomics method to clarify the major functional components. Finally, the effects of exogenous redox mediators on biofilm growth and PAHs degradation will be investigated to further explore influences of extracellular electron transfer on PAHs biodegradation. The results of this study will benefit for microbial remediation of soil PAHs pollution.

微生物膜具有高效降解多环芳烃(PAHs)的能力，然而其降解过程及机理仍不明确。微生物胞外电子传递是有机污染物降解等环境生物化学过程的重要驱动力，探明生物膜胞外电子传递及其在PAHs降解过程中的作用有助于揭示其高效降解机制。本项目围绕降解菌生物膜胞外电子传递与PAHs降解相互作用进行研究，借助环境扫描电镜和红外光谱等分析手段监测降解菌生物膜形态结构特征；采用生物化学和电化学方法探究微生物膜和胞外聚合物氧化还原活性，揭示降解菌生物膜电子传递特征；通过对PAHs降解动力学过程的细致监测，构建胞外电子传递与PAHs降解的关系曲线，揭示二者耦合关系及相互影响；采用蛋白质组学等技术分析胞外聚合物功能蛋白表达特征，揭示胞外聚合物在电子传递以及PAHs降解过程中的重要作用；阐明外源氧化还原介体调控胞外电子传递对微生物膜生长和PAHs降解的影响和机理，为微生物修复PAHs污染土壤提供理论依据和技术支撑。

微生物膜具有高效降解多环芳烃(PAHs)的能力，然而其降解过程及机理仍不明确。微生物胞外电子传递是有机污染物降解等环境生物化学过程的重要驱动力，探明生物膜胞外电子传递及其在PAHs降解过程中的作用有助于揭示其高效降解机制。本项目研究了不同有机和无机载体（蒙脱石、针铁矿、玉米秸秆生物炭）生物膜体系下PAHs降解的动力学过程，结果表明蒙脱石和生物炭显著提高了微生物对菲的降解效率，同时促进了胞外聚合物（EPS）中多糖和蛋白质组分的增加，但针铁矿对菲生物降解和EPS产生的促进作用较弱。扫描电镜结果显示菲降解过程中降解菌在生物炭载体表面附着生长数量最多，形态最优。研究了金属离子 (Na(I)、Ni(II)、Co(II)、Cu(II)、Fe(III))饱和修饰的蒙脱石矿物上微生物对芘的生物降解特征，揭示了表面金属离子对蒙脱石体系芘的生物降解有显著影响，降解效率依次为Fe(III)>Na(I)≈Co(II)>Ni(II)≈Cu(II)。生物电化学分析表明，不同金属改性蒙脱石的电子传递活性(给电子容量和电子传递系统活性)不同，且与芘的生物降解密切相关。Fe(III)修饰极大地激发了降解酶(过氧化物酶和双加氧酶)活性和电子转移活性，从而增强了芘的生物降解能力。细菌胞外蛋白和腐殖质在胞外电子传递过程中起重要作用。膜结合细胞色素C蛋白和细胞外核黄素被证实为电子穿梭体，分别负责跨膜和跨细胞外基质的电子传递。核黄素、腐殖酸和铁氰化钾等外源电子传递介质能够加速芘的生物降解，进一步证实了胞外电子传递在细菌-矿物界面调控PAHs降解转化中的重要作用，为微生物高效降解有机污染物提供了新的见解。