多组学技术联合解析河流微生物群落对氮添加的响应

Eutrophication (especially the enrichment of nitrogen and phosphorous) is one of the major threats faced by river ecosystems. Being a crucial component of river ecosystem, microbes could be used as bio-indicators to represent the health of rivers. Microbes present in different riverine sections also show adaptation to nutrient pollution and possess the potential to treat water pollution. However, it remains unclear about the processes and mechanisms of riverine microbial responses to water pollution. In this study, we aim to collect original microbial communities from a highly polluted wastewater-receiving river, the North Canal River, running through Beijing and Tianjin. Those microbial communities will be exposed to different levels of nitrogen addition in experiments. Variations of community composition before and after treatment will be detected via metagenomics, mainly 16S rRNA sequencing in this study. Variations of community transcripts before and after treatment will be detected via metatranscriptomics. Protein-level variations before and after treatment will be detected via metaproteomics. We also aim to combine these variations with water physicochemical parameters to identify key drivers of community dynamics. With a simplified system, we aim to analyze the processes and mechanisms of microbial communities to different levels of nitrogen addition. With this study, we hope to promote the understanding about the ecological effects of water pollution on aquatic organisms.

富营养化（尤其是氮磷富集）是河流水体面临的重要威胁之一。作为河流生态系统的重要组分，微生物既可以用于指征水体健康状态，又在水体治理中具有重大潜力。然而，目前对于微生物群落响应水体污染的过程与机制仍然缺乏充分的认识。本研究拟以重度污染的北运河为例，以不同污染程度下的原位微生物群落为研究对象，在实验室进行不同浓度的氮添加控制实验，研究微生物群落对不同程度污染的适应过程与机制。通过宏基因组学分析，解析培养前后群落组成与结构的差异；通过宏转录组学分析，解析培养前后群落转录本的差异；通过宏蛋白质组学分析，解析培养前后群落的蛋白表达差异。同时耦合水质理化指标进行多重统计分析，识别在不同层次驱动群落演替的关键因子。本项目在简化处理的条件下，解析原位微生物群落对氮浓度梯度的响应过程与机制，可以加深对污染水体的群落生态学效应的理解与认识。

营养污染是水体生态系统及其生物多样性面临的主要威胁之一。然而，目前对河流水体的污染生态学效应，尤其是微小型生物的响应机制，仍然缺乏足够的认知。这一缺乏，也显著制约了相关预警与治理方案的制定和实施。为此，本项目主要围绕“水体污染影响河流生态系统的过程和机制”这一科学问题展开，重点剖析：氮富集能否驱动浮游微生物群落的定向演替，并解析相关机制。结果发现，氮浓度（总氮，TN）较高的水体环境，会显著富集β-变形菌，暗示氮污染可能驱动了群落的定向演替。浮游微生物群落整体的组成结构与水体环境的理化性质具有显著相关性；驱动群落演替的主导生态学过程是同质化选择，关键驱动因素是TN。随着TN浓度升高，群落污染指数增大，支持了微生物群落对TN的适应性响应。此外，TN浓度升高，还导致微生物群落的功能多样性降低、物种互作复杂度降低。这意味着，高氮情境下的微生物群落具有更低的稳定性和更弱的恢复力，在环境继续恶化的情况下，更容易崩溃。最后，在微生物群落中检测到至少48个含潜在病原微生物的属，并且其相对多度随TN浓度的升高而明显增大。综上，TN浓度增大明显驱动了微生物群落的定向演替，具体表现为：物种组成、群落功能和生物互作的趋简性；群落更易富集潜在病原微生物，并给人类健康带来巨大风险。项目研究成果对污染水体的生物多样性监测和治理以及人体健康风险评估具有一定的指导意义。