养殖尾水处理系统填料生物膜氮循环微生物功能特征

为探讨填料生物膜在养殖尾水处理中对水体氮循环的影响机制，采用16S rRNA基因扩增子测序和宏基因组测序技术，对填料生物膜、水体细菌的群落结构及其与氮循环相关的功能基因丰度差异特征进行了研究。结果显示，填料生物膜微生物主要参与氮代谢活动。在属水平上，Pseudomonas、Spirochaeta、Opitutus和Syntrophus是填料生物膜氮素转化过程的重要功能微生物类群。与水体相比，填料生物膜的碳代谢活动能力较强（P<0.05）；填料生物膜上固氮功能基因nifH、硝化功能基因hao、反硝化和异化硝酸盐功能基因napA、nirS、norB、norC、nrfA、nirB和氮代谢调控基因ntrC及其相应的关键酶均显著高于周围水体（P<0.05），且对含氮污染物有显著去除效果。研究表明，养殖尾水处理系统内复合填料生物膜具有比周围水环境更强的氮周转能力，主要通过关键功能物种介导的固氮和反硝化作用实现养殖尾水氮素的转化和迁移。研究结果作为野外实验证据，可为复合填料生物膜系统在水产养殖尾水治理中的应用提供理论依据。

Functional Characteristics of Nitrogen Cycling Microbes in the Biofilm Carrier of an Aquaculture Tailwater Treatment System

The pollution of aquaculture tailwater has become an important factor restricting the development of the aquaculture industry. The biofilm carrier in the aquaculture tailwater treatment system is an economical and efficient treatment facility developed in recent years to remove pollutants from aquaculture wastewater. However, little is known about microbial ecological effects and functions of the biofilm carrier during nitrogen migration and transformation. In this study, we utilized a metagenomic approach to dissect nitrogen cycling processes and their underlying driving mechanisms in microbial communities of the biofilm carrier. It was found that the biofilm microbes were mainly involved in nitrogen metabolism activities. Compared with the water body, the carbon metabolism activity of the biofilm carrier was stronger (P<0.05). Moreover, the relative abundance of the hydroxylamine reductase with nitrification, nitrous oxide reductase and nitric oxide reductase with denitrification and their encoded functional genes nosZ and norB, and nitrite reductase with dissimilatory nitrate reduction and functional genes napA, nrfA and nirB, as well as nitrogenase and functional gene nif HDK were relatively high (P<0.05), indicating that the biofilm microbes had a stronger nitrogen turnover capacity than the surrounding water environment. The genus Pseudomonas, Spirochaeta, Opitutus and Syntrophus were important functional microbial groups in the key process of nitrogen transformation in biofilm carriers. The above research results showed that the biofilm microbes in the aquaculture tailwater treatment system were mainly involved in the transformation and migration of nitrogen through nitrogen fixation and denitrification mediated by key functional species. The results of this study, as field experimental evidence, can provide a theoretical basis for the future practice of biofilm carrier systems in aquaculture tailwater treatment.