ABSTRACT: The effects of ammonium on biofilm attached to submerged macrophytes remain unclear. We studied the microbial communities of epiphytic biofilms on the leaf surface of Hydrilla verticillata under increasing ammonium loadings using 16S rRNA gene sequencing and RT-PCR. The study showed that the microbial community structures were influenced by increased ammonium loadings. N-cycling bacteria including the nitrifier Nitrospira and the denitrifiers Rhodobacter, Hyphomicrobium, and Flavobacterium were found to be predominant. Copy numbers of Ncycling functional genes (including amoA, nxrA, narG, napA, nirK, nirS, qnorB, and nosZ) were stimulated by increased ammonium loadings, showing the high potential of attached biofilms in removing ammonium-N through coupled nitrification-denitrification. Our results indicated that submerged macrophytes facilitated the ammonium removal process not only by providing favorable surface niches for ammonium oxidizers, nitrifiers, and denitrifiers in the attached biofilms but also by mediating dissolved oxygen concentrations and alkalinity condition in the water.

中文翻译：

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铵盐负荷驱动淹没在大型植物Hydrilla verticillata上的生物膜中的细菌群落转移

摘要：铵对附着在沉水植物上的生物膜的影响尚不清楚。我们使用16S rRNA基因测序和RT-PCR研究了在铵盐负荷增加的情况下，褐藻（Hydrilla verticillata）叶片表面的附生生物膜的微生物群落。研究表明，微生物群落结构受到铵盐含量增加的影响。N循环细菌占主导地位，其中包括硝化硝化硝化细菌和反硝化细菌红细菌，Hyphomicrobium和黄杆菌。Ncycling功能基因的拷贝数（包括amo A，nxr A，nar G，nap A，nir K，nir S，qnor B和nos Z）受到铵盐含量增加的刺激，显示出附着的生物膜在通过耦合硝化-反硝化作用去除铵​​态氮方面具有很高的潜力。我们的研究结果表明，淹没的大型植物不仅为附着的生物膜中的铵氧化剂，硝化剂和反硝化剂提供了有利的表面生态位，而且还通过介导水中的溶解氧浓度和碱度条件促进了铵的去除过程。