养殖尾水浮床处理系统水生植物根际细菌的氮循环作用机制

Regulation of bacterial nitrogen cycle of aquatic plants rhizosphere in the ecological floating bed system for aquaculture tailwater treatment

为探讨养殖尾水处理中浮床水生植物根际细菌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方法,对浮床水生植物黄花鸢尾(Iris wilsonii C.H.Wright)根际细菌、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。结果表明:生态浮床水生植物根际细菌以变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、Patescibacteria门和拟杆菌门(Bacteroidota)为主要优势门类;在属水平上,有10种关键功能菌属在氮素迁移转化关键过程中发挥了重要作用;与水体相比,水生植物根际细菌多样性较高,氮代谢活动更为活跃(P<0.05),且主要参与碳代谢、转运蛋白、细菌双组分调节系统和群体感应等代谢功能途径;根际细菌固氮功能基因(nifH、nifD和nifK)、硝化作用功能基因(hao)、反硝化作用功能基因(nirS、norB和nosZ)、异化/同化硝酸盐还原基因(napA、nrfA、nirB和nasA)及其6个氮循环关键酶的相对丰度均显著升高(P<0.05)。研究表明,生态浮床水生植物根际的氮素周转能力强于周围水环境,其生物脱氮的最主要方式是反硝化和异化硝酸盐还原过程。

In order to explore the influence mechanism of 250 m^(2)floating bed aquatic plants on nitrogen cycle of water bodies by rhizosphere bacteria in the aquaculture tailwater treatment,the differences in the bacterial composition and functional genes related to nitrogen cycling were monthly investigated in front,center,and rear in the aquatic plant Iris wilsonii C.H.Wright floating beds from May to August 2020 by 16S rRNA gene amplicon sequencing and metagenomic sequencing technology.Results showed that Proteobacteria,Firmicutes,Patescibacteria,and Bacteroidota were found to be the dominant phyla in the rhizosphere of Iris wilsonii C.H.Wright roots during the experiment period.At genus level,10 core functional microorganisms played an important role in the key process of nitrogen migration and transformation in aquaculture tailwater.There was higher microbial diversity and more active nitrogen metabolism activity,primarily in metabolic pathways or functions such as carbon metabolism,ABC transport protein,bacterial two component system and Quorum sensing,in the aquatic plant rhizosphere than those in the floating bed water bodies(P<0.05).Moreover,the relative abundance of rhizosphere nitrogen fixation function genes(nifH,nifD and nifK),nitrification function gene(hao),denitrification function genes(nirS,norB and nosZ),dissimilatory/assimilated nitrate reduction genes(napA,nrfA,nirB and nasA)and their key enzymes in the nitrogen cycle were significantly increased(P<0.05).The rhizosphere microbes of the aquatic plants had stronger nitrogen turnover capacity than that in the surrounding water environment,and microbial denitrification and dissimilatory nitrate reduction process were the main denitrification pathways of the rhizosphere effect of the ecological floating bed aquatic plants.