Purpose

Complete ammonia oxidizers (comammox), which convert ammonia to nitrate through nitrite, are a newly discovered nitrifying group. In recent years, comammox Nitrospira have been discovered in various natural and engineered ecosystems. However, little is known about the distribution dynamics of comammox Nitrospira in estuary tidal flat sediments.

Materials and methods

Chongming eastern tidal flat, the largest tidal flat in the Yangtze River Estuary, was selected as the research area. Through a combination of molecular biology assays, phylogenetic analysis based on functional gene sequences and statistical correlation with physicochemical properties, we determined the distribution and diversity of comammox Nitrospira in Chongming eastern tidal flat and analyzed the potential influencing environmental factors.

Results and discussion

The results indicated comammox Nitrospira were widely distributed in Chongming eastern tidal flat, while with lower abundance than the ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Clade A1 comammox Nitrospira showed adaptation to relatively high salinity, and was more distributed in middle and low tidal flats, while clade A2 and clade A3 were mostly distributed in high tidal flats with low salinity. The abundance and community structure of comammox Nitrospira were mainly affected by salinity, ammonia concentration, and temperature.

Conclusion

This study showed the general existence of comammox Nitrospira in Chongming eastern intertidal sediments and indicated that the differences of tidal locations, which lead to a gradient in the physicochemical properties of the sediments, in turn affects the spatial distribution of comammox Nitrospira in estuary tidal flats.

中文翻译：

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崇明东部潮间沉积物氨硝氮的群落结构和丰度。

目的

完全氨氧化剂（comammox）是通过新发现的硝化基团，它通过亚硝酸盐将氨转化为硝酸盐。近年来，已在各种自然和工程生态系统中发现了昏迷硝化螺菌。但是，关于河口潮滩沉积物中的comammox Nitrospira分布动态知之甚少。

材料和方法

长江口最大的滩涂崇明东滩被选为研究区域。通过分子生物学分析，基于功能基因序列的系统发育分析以及与理化性质的统计相关性的组合，我们确定了崇明东部潮滩中的comammox Nitrospira的分布和多样性，并分析了潜在的影响环境因素。

结果和讨论

结果表明，在崇明东部的滩涂中，昏迷的硝化螺菌分布较广，但其丰度却低于氨氧化细菌（AOB）和氨氧化古细菌（AOA）。进化枝A1昏迷硝化螺菌显示出对较高盐度的适应性，并更多地分布在中低潮滩上，而进化枝A2和进化枝A3主要分布在低盐度高潮滩上。昏迷硝化螺菌的丰度和群落结构主要受盐度，氨浓度和温度的影响。

结论

这项研究表明崇明东部潮间带沉积物中普遍存在昏迷硝化螺菌，并指出潮汐位置的不同会导致沉积物的理化性质出现梯度，进而影响河口滩涂中的昏迷硝化螺菌的空间分布。