生态浮床池塘水体核心微生物种类及氮循环功能研究

为探索生态浮床池塘水体微生物对氮循环的贡献及其潜在驱动机制，本研究采用16S rRNA基因扩增子测序和宏基因组测序技术联合解析有无生态浮床水体中微生物群落结构及氮循环功能差异。群落结构分析结果表明，与无浮床水体相比，浮床水体中变形菌门（Proteobacteria）微生物占主要优势。微生物群落结构发生明显改变，浮床水体中C39、甲基杆菌属（Methylobacter）、栖湖菌属（Limnohabitans）、多核杆菌属（Polynucleobacter）和黄杆菌属（Flavobacterium）的相对丰度显著增加（P<0.05）。试验期间，浮床水体微生物Shannon多样性指数显著降低（P<0.05），而Chao丰富度指数显著升高（P<0.05）。甲基杆菌、热单胞菌（Caldimonas）和伯克氏菌（Bulkholderia）是浮床水体脱氮过程中关键核心微生物组。氮循环功能研究结果表明，铺设生态浮床后，浮床水体氮代谢活动能力显著增强（P<0.05），以固氮（nifH、nifD、nifK）、反硝化（narG、napA、nirS、norB和nosZ）和异化硝酸盐还原过程（nrfA、nrfH）为主的氮循环功能基因丰度显著提高（P<0.05）。核心微生物组促进了水体生物固氮、反硝化和异化硝酸盐还原过程，提升了养殖池塘水体氮循环的能力，显著降低了池塘水体中总氮、硝态氮和亚硝态氮含量（P<0.05）。研究表明，生态浮床核心微生物组介导的固氮和反硝化作用是实现池塘水体氮素转化和迁移的重要途径，促进了养殖池塘水体氮循环，有利于养殖池塘生态环境保护和含氮污染物的去除。

Core microbiome and nitrogen cycling in ecological floating-bed ponds

To explore the contribution of microorganisms to the nitrogen cycle and the potential driving mechanism in ecological floating bed ponds, 16S rRNA gene amplicon sequencing and metagenomic sequencing technology were used to analyze the characteristics of microbial community structure and nitrogen cycling function. Compared with the non-floating-bed water, Proteobacteria dominated in the floating bed water microbial community. The microbial community structure changed significantly, as the relative abundances of C39, Methylobacter, Limnohabitans, Polynucleobacter and Flavobacterium in the floating bed water were significantly increased (P<0.05). During the experiment, microbial alpha diversity Shannon index decreased significantly (P<0.05). However, the Chao richness index increased significantly in the floating-bed ponds (P<0.05). At the genus level, Methylobacter, Caldimonas, and Bulkholderia were the core microbiomes in the denitrification process. Nitrogen cycling results revealed nitrogen metabolism activity significantly increased in the floating-bed ponds (P<0.05). The nitrogen fixation gene nifH, nifD, and nifK, denitrification genes narG, napA, nirS, norB, and nosZ, and dissimilatory nitrate reduction gene nrfA and nrfH were all significantly increased in relative abundance (P<0.05). The core microbiomes promoted the biological nitrogen fixation, denitrification, and dissimilatory nitrate reduction processes, improved the capacity of nitrogen cycling, and significantly reduced the contents of total nitrogen, nitrate nitrogen and nitrite nitrogen in the ecological floating-bed ponds (P<0.05). Our study has shown that nitrogen fixation and denitrification mediated by the core microbiome is the important way to realize the transformation and migration of nitrogen in ecological floating bed ponds, which promotes the nitrogen cycle and is beneficial to the environment protection and nitrogen pollutants removal.