School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510006, China.
School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou 510006, China.
Water Res. 2022 Aug 15;222:118857. doi: 10.1016/j.watres.2022.118857. Epub 2022 Jul 12.
Urban rivers are hotspots of regional nitrogen (N) pollution and N transformations. Previous studies have reported that the microbial community of urban rivers was different from that of natural rivers. However, how microbial community affects N transformations in the urban rivers is still unclear. In this study, we employed N nutrients-related isotope technology (includes natural-abundance isotopes survey and isotope-labeling method) and bioinformatics methods (includes 16S rRNA high-throughput sequencing and quantitative PCR analysis) to investigate the major N transformations, microbial communities as well as functional gene abundances in a metropolitan river network. Our results suggested that the bacterial community structure in the highly urbanized rivers was characterized by higher richness, less complexity and increased abundances of nitrification and denitrifying bacterium compared to those in the suburban rivers. These differences were mainly caused by high sewage discharge and N loadings. In addition, the abundances of nitrifier gene (amoA) and denitrifier genes (nirK and nirS) were significantly higher in the highly urbanized rivers (2.36 × 10, 7.43 × 10 and 2.28 × 10 copies·mL) than that in the suburban rivers (0.43 × 10, 2.18 × 10 and 0.99 × 10 copies·mL). These changes in microbes have accelerated nitrification-denitrification processes in the highly urbanized rivers as compared to those in the suburban rivers, which was evidenced by environmental isotopes and the rates of nitrification (10.52 vs. 0.03 nmol·L·h) and denitrification (83.31 vs. 22.49 nmol·g·h). Overall, this study concluded that the excess exogenous N has significantly shaped the specific aquatic bacterial communities, which had a potential for enhancing nitrification-denitrification processes in the highly urbanized river network. This study provides a further understanding of microbial N cycling in urban river ecosystems and expands the combined application of isotopic technology and bioinformatics methods in studying biogeochemical cycling.
城市河流是区域氮（N）污染和 N 转化的热点。先前的研究报告表明，城市河流的微生物群落与自然河流不同。然而，微生物群落如何影响城市河流中的 N 转化仍不清楚。在这项研究中，我们采用 N 营养相关同位素技术（包括自然丰度同位素调查和同位素标记方法）和生物信息学方法（包括 16S rRNA 高通量测序和定量 PCR 分析）来研究大都市河流网络中的主要 N 转化、微生物群落以及功能基因丰度。我们的结果表明，与郊区河流相比，高度城市化河流中的细菌群落结构具有更高的丰富度、更少的复杂性和硝化和反硝化细菌的丰度增加。这些差异主要是由高污水排放量和 N 负荷造成的。此外，高度城市化河流中的硝化菌基因（amoA）和反硝化菌基因（nirK 和 nirS）的丰度（2.36×10、7.43×10 和 2.28×10 拷贝·mL）明显高于郊区河流（0.43×10、2.18×10 和 0.99×10 拷贝·mL）。与郊区河流相比，这些微生物的变化加速了高度城市化河流中的硝化-反硝化过程，这一点可以通过环境同位素和硝化（10.52 对 0.03 nmol·L·h）和反硝化（83.31 对 22.49 nmol·g·h）的速率得到证明。总体而言，本研究得出结论，过量的外源 N 显著塑造了特定的水生细菌群落，这有可能增强高度城市化河流网络中的硝化-反硝化过程。本研究进一步了解了城市河流生态系统中的微生物氮循环，并扩展了同位素技术和生物信息学方法在研究生物地球化学循环中的综合应用。
