蓝藻活性物质对富营养化表层水体反硝化作用影响及机制

Denitrification is the main way of self-purification of eutrophic water body, which is an organic substance decomposition process with nitrate as electron acceptor. Cyanobacteria growth and cell degradation produce a large number of organic bioactive substance, and cyanobacteria bloom caused the change of organic substance source in the eutrophic surface water. However the effect of cyanobacterial bioactive substance on the process of denitrification drove by heterotrophic microorganisms denitrification is still not clear. This research is proposed to carry out microcosm experiment to study the effect of bioactive organic substance, which produced from the dominant cyanobacteria species in the eutrophic lakes of china on the community structure of denitrifying bacteria, the transcriptional abundance of denitrifying genes, the activity of denitrifying enzymes and the reaction degree of denitrification with the aid of functional gene high-throughput sequencing, qRT - PCR and stable isotope 15N tracer technique, in eutrophic surface water with the characteristics of high dissolved oxygen and high pH. The research will try to clarify whether cyanobacterial bioactive substance can change the community structure of denitrifying bacteria and the transcriptional abundance of denitrifying genes, thereby further affected denitrifying process for offering theoretical basis on the effect and mechanism of cyanobacteria bloom on nitrogen cycle in eutrophic surface water.

反硝化是水体氮素自净的主要途径，本质是以硝态氮为电子受体的有机物质分解过程。水体蓝藻暴发引起表层水体有机物质来源的改变，蓝藻生长和细胞降解过程中产生大量活性有机物质，然而其对异养微生物驱动的反硝化过程的影响仍不清楚。本申请拟开展微宇宙实验，借助功能基因扩增子高通量测序、荧光定量反转录PCR（qRT-PCR）以及稳定性同位素15N示踪技术，研究在富营养化表层水体高溶解氧、高pH的特征环境下，我国淡水湖泊优势蓝藻物种分泌和细胞降解产生的活性物质对水体反硝化细菌群落结构、功能基因转录表达、反硝化酶系活性、反硝化反应进行程度（15N2O:15N2）的影响。通过研究，期望阐明蓝藻活性有机物质是否能够改变水体中反硝化细菌种群结构并干预反硝化功能基因的转录表达,从而进一步影响反硝化反应过程，为蓝藻暴发对水体氮素循环的影响及机制提供理论基础。

反硝化是水体氮素自净的主要途径，本质是以硝态氮为电子受体的有机物质分解过程。水体蓝藻暴发引起表层水体有机物质来源的改变，蓝藻生长和细胞降解过程中产生大量活性有机物质，然而其对异养微生物驱动的反硝化过程的影响仍不清楚。DNA-SIP结果表明富营养化表层水体中确实存在大量且丰富的直接或间接利用蓝藻分泌或细胞降解释放有机物的细菌，在门水平上Betaproteobacteria是该类细菌的优势物种。 qPCR和基于反硝化功能基因nirK, nirS和nosZ高通量测序结果表明，富营养化表层水体反硝化功能基因nirK, nirS和nosZ的丰度与蓝藻生物量成正相关性，而且以nirK, nirS和nosZ为表征的反硝化细菌群落结构随着蓝藻暴发的不同时期而变化。微宇宙实验结果表明，借助功能基因扩增子高通量测序、荧光定量反转录PCR（qRT-PCR）以及稳定性同位素15N示踪技术，发现在富营养化表层水体高溶解氧、高pH的特征环境下，我国淡水湖泊优势蓝藻物种分泌和细胞降解产生的不同活性物质对水体反硝化细菌群落结构、功能基因转录表达、反硝化酶系活性、反硝化反应进行程度（15N2O:15N2）产生了不同效果的强烈影响。通过研究，阐明了蓝藻分泌和细胞降解产生的活性有机物质能够改变水体中反硝化细菌种群结构并干预反硝化功能基因的转录表达,从而进一步影响反硝化反应过程，研究结果为蓝藻暴发对水体氮素循环的影响及机制提供理论基础。