Tan Qiuyang, Zhu Yi, Zhao Yinjun, Zheng Lei, Wang Xue, Xing Yuzi, Wu Haoming, Tian Qi, Zhang Yaoxin
College of Water Science, Beijing Normal University, Beijing 100875, PR China.
Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Ministry of Education, Nanning Normal University, Nanning 530001, PR China.
Water Res. 2025 Apr 1;273:122964. doi: 10.1016/j.watres.2024.122964. Epub 2024 Dec 17.
Ammonia oxidizers are key players in the biogeochemical nitrogen cycle. However, in critical ecological zones such as estuaries, especially those affected by widespread anthropogenic dam control, our understanding of their occurrence, ecological performance, and survival strategies remains elusive. Here, we sampled sediments along the Haihe River-Estuary continuum in China, controlled by the Haihe Tidal Gate, and employed a combination of biochemical and metagenomic approaches to investigate the abundance, activity, and composition of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and complete ammonia oxidizers (comammox). We also conducted an extensive comparison of the salinity adaptation mechanisms of different ammonia oxidizers. We found that AOB (57.55 ± 11.46 %) dominated the nitrification process upstream of the tidal gate, while comammox (68.22 ± 14.42 %) played the major role downstream. Redundancy analysis results showed that total nitrogen, ammonium, and salinity were the primary factors influencing the abundance, activity, and contribution of ammonia oxidizers. The abundance and activity of AOB were significantly positively correlated with ammonium. KEGG annotation results showed that AOA Nitrososphaera, AOB Nitrosomonas, and comammox Nitrospira had 7, 31, and 22 genes associated to salinity adaptation, respectively, and were capable of employing both the "salt-in" and "salt-out" strategies. Metagenome assembly results indicated that comammox outperformed AOA primarily in compatible solute accumulation; AOA can synthesize glutamate, whereas comammox Nitrospira can additionally synthesize glycine betaine, choline, and trehalose. The tidal gate caused sharp shifts in ammonium (from 4.10 ± 3.28 mg·kg to 0.45 ± 0.10 mg·kg) and salinity (from 1.64 ± 0.48 ppt to 3.26 ± 0.89 ppt), playing a dominant role in driving niche differentiation of ammonia oxidizers along the Haihe River-Estuary continuum. These findings provide profound insights into the nitrogen cycle in freshwater-saltwater transition zones, especially in today's world where estuaries are widely controlled by tidal gates.
氨氧化菌是生物地球化学氮循环的关键参与者。然而，在河口等关键生态区域，尤其是那些受到广泛人为水闸控制影响的区域，我们对它们的存在、生态表现和生存策略的了解仍然有限。在此，我们在中国受海河防潮闸控制的海河河口连续区域采集沉积物样本，并采用生化和宏基因组学方法相结合的方式，研究氨氧化古菌（AOA）、氨氧化细菌（AOB）和全程氨氧化菌（comammox）的丰度、活性和组成。我们还对不同氨氧化菌的盐度适应机制进行了广泛比较。我们发现，AOB（57.55 ± 11.46%）在防潮闸上游的硝化过程中占主导地位，而comammox（68.22 ± 14.42%）在下游起主要作用。冗余分析结果表明，总氮、铵和盐度是影响氨氧化菌丰度、活性和贡献的主要因素。AOB的丰度和活性与铵显著正相关。KEGG注释结果表明，AOA亚硝化球菌属、AOB亚硝化单胞菌属和comammox硝化螺菌属分别有7、31和22个与盐度适应相关的基因，并且能够采用“盐进”和“盐出”策略。宏基因组组装结果表明，comammox在相容性溶质积累方面主要优于AOA；AOA可以合成谷氨酸，而comammox硝化螺菌属还可以合成甘氨酸甜菜碱、胆碱和海藻糖。防潮闸导致铵（从4.10 ± 3.28 mg·kg降至0.45 ± 0.10 mg·kg）和盐度（从1.64 ± 0.48 ppt升至3.26 ± 0.89 ppt）急剧变化，在驱动海河河口连续区域氨氧化菌的生态位分化方面起主导作用。这些发现为淡水-咸水过渡区的氮循环提供了深刻见解，尤其是在当今河口受到水闸广泛控制的世界中。
