多环芳烃引起的水体氮转化胁迫效应及沉水植物生物膜响应调控机制研究

Aerobic environment and high redox potential are conducive to the aerobic transformation of PAHs and nitrogenous compounds, submerged plants mostly have the secrete oxygen ability of root and foliar, which is conducive to the formation of micro-region aerobic environment and biofilm in polluted water, but it usually is affected by the coexistence of pollutants (e.g. PAHs and nitrogenous compounds)in the process of biofilm formation, and then affects the dissipation and accumulation of these pollutants. The response and regulation mechanisms are rarely reported in domestic and foreign. My preliminary study found that the existence of trace PAHs (100ppb) could induce the accumulation of nitrogenous compounds in water and sediment, but the influence mechanism is not clear. This project aimed at the coexistence characteristics of PAHs, nitrogen and submerged plants in polluted water, taking the biofilm attached on submerged plants which having significant influence on pollutants degradation as the breakthrough point, using Two Photon Laser Confocal Scanning Microscopy, scanning electron microscopy, molecular biology technology of High-throughput sequencing and metagenomics methodology, through the coupling analysis among the water habitats, foliar biofilm community structure and functional gene diversity of degradation bacteria, quorum sensing signal in different treatments, we could resolve the effect of PAHs on nitrogen cycle in water and the response-regulation mechanisms of biofilm on submerged plants from the molecular and subcellular level analysis, based on the mechanism analysis of “submerged plants secrete oxygen-aerobic biological membrane construction - the response and regulation of microorganism – pollutant dissipation in water body”, and to provide a theoretical basis for the water environment remediation technology with efficient, economic and ecological security.

好氧及高氧化还原电位有利于多环芳烃（PAHs）及氮的好氧转化，沉水植物大多具有根系及叶面泌氧能力，有利于微域好氧及相应生物膜形成，但其形成会受到共存污染物（如PAHs及氮）的调控并影响污染物的消解和累积，这种响应调控机制国内外鲜有报道。申请人前期研究发现,水体痕量PAHs的存在（100ppb）可导致水体中氮的累积,但具体机理尚不清楚。本项目针对污染水体中PAHs、氮与沉水植物共存特征，以可对污染物转化产生重大影响的沉水植物生物膜为切入点，借助激光共聚焦、扫描电镜、高通量及宏基因组分子生物学等技术，通过对水生境、营养盐、叶面生物膜群落结构、功能基因多样性、群体感应信号分子的跟踪及耦合分析，可从分子水平解析PAHs对水体氮循环的影响以及生物膜的响应调控机制，拟通过对"沉水植物泌氧-好氧生物膜构建-微生物响应调控-水体污染物削减"作用机理的解析，为高效、经济与生态安全的水环境修复提供理论依据。

沉水植物表面附着的大量生物膜，在污染物的消解方面发挥着重要作用。而多环芳烃（PAHs）是一类广泛存在于水土环境中的持久性有机污染物和已知数量最多的致癌物，其对人类神经管先天缺陷、生育先天缺陷以及癌症的诱导作用等特点，已受到各国政府和科学界的广泛关注。近年来，我国的河湖水体普遍受到PAHs的污染，部分地区甚至危及到水产品的安全。近年来，本课题组前期研究发现，痕量PAHs在水体中的存在，就可对水体的氮转化循环造成抑制和胁迫，造成水体中氮的累积和严重富营养化，但如果有沉水植物的存在，可缓解PAHs引起的对氮转化的抑制和胁迫效应，但具体机制尚不清楚。如何充分利用河湖原生生态系统如沉水植物及其表面附着生物膜的自净功能，通过定向人为诱导构建适合高效、经济与生态安全的污染物去除技术，阻断有毒PAHs通过水生食物链进入人体，以及缓解其对水体氮转化的抑制效应，已成为这些环境污染控制技术进一步发展的瓶颈和研究热点，也是关系到国计民生和国家长治久安的一件大事。.本项目针对污染水体中PAHs、氮与沉水植物共存特征，以可对污染物转化产生重大影响的沉水植物生物膜为切入点，借助激光共聚焦、扫描电镜、高通量及宏基因组分子生物学等技术，通过对水生境、营养盐、叶面生物膜群落结构、功能基因多样性、群体感应信号分子的跟踪及耦合分析，从分子水平解析PAHs对水体氮循环的影响以及生物膜的响应调控机制。结果表明，沉水植物可通过泌氧及对水体理化因子的调控（如溶氧、pH和氧化还原电位的提升），营造有利于PAHs-氮耦合消解功能菌生物膜形成的良性生境，生物膜中的PAHs和氮转化菌群相对于无沉水植物体系均发生转变（如由固氮捲菌属和固氮弧菌属转变为根瘤杆菌；而PAHs降解菌如新鞘氨醇杆菌属和鞘氨醇单胞菌属丰度则提升），提升了叶面生物膜的抗胁迫性和降解能力，达到PAHs-氮耦合消解的同时实现，实现水体有机高风险PAHs有效消解及同时脱氮的高效耦合作用，本项目的研究成果可为高效、经济与生态安全的水环境修复技术的提出提供理论依据。