锡林河流域Nitrospira的生态位分化及环境驱动力

Niche differentiation of Nitrospira and associated environmental driving forces in Xilin river basin

摘要:

【背景】硝化螺菌属(Nitrospira)驱动的全程及半程硝化过程在全球氮循环中发挥关键作用，但关于锡林河流域Nitrospira的生态位分化和环境驱动力及其可能发挥的全程硝化功能尚不明晰。【目的】阐明锡林河流域不同生境Nitrospira的生态位分化及环境驱动力，探究可能的全程硝化功能。【方法】利用16S rRNA基因高通量测序及生物信息学分析研究不同生境沉积物及土壤Nitrospira类群的组成、丰度、生态位分化及其环境驱动力，并预测其全程硝化功能。【结果】共检测到9类Nitrospira，其中Nitrospira 1、2、4主要分布在旱生环境，与沙粒、水分含量、pH及氨氮间存在负相关关系，与硝态氮、可溶性盐、总有机碳、全氮、全磷、粉粒和粘粒含量间存在正相关关系；Nitrospira 5、6、7、8、9主要分布在水生及湿生环境，与粉粒等存在负相关关系，与沙粒等存在正相关关系(Nitrospira 9与氨氮存在负相关除外)；Nitrospira 3优先分布在河床中心水生环境，仅与沙粉粒含量存在正相关关系，与其他环境因子存在负相关关系。【结论】锡林河流域Nitrospira类群有明显的生态位分化和广泛的生境适应性。Nitrospira 1、2、4最适于营养相对丰富的旱生环境；Nitrospira 5、6、7、8、9最适于相对寡营养的水生及湿生环境；Nitrospira 3偏爱粉沙、自由水及低氨寡营养水生环境。粉粒含量、可溶性盐和氨氮是导致Nitrospira类群生态位分化及空间分异的最主要环境驱动力。推测Nitrospira 3很可能是驱动全程硝化的完全氨氧化菌(comammox)，而Nitrospira 1、2、4、5、6、7、8、9是否为Comammox有待探究。

关键词:锡林河流域，硝化螺菌属，生态位分化，环境驱动力，完全氨氧化菌

Abstract:

[Background] Complete and incomplete nitrification driven by Nitrospira plays a key role in global nitrogen cycle, but little is known about the niche differentation of Nitrospira, and associated environmental driving forces for Nitrospira’s niche separation and as well as possible functions like complete nitrification driven by Nitrospira in Xilin river basin. [Objective] To reveal the niche differentiation of Nitrospira and associated environmental driving forces, and deciphering the possible functions like complete nitrification driven by Nitrospira. [Methods] Based on high throughput sequencing of 16S rRNA gene with bioinformatics analysis, the compositions and abundance of sediment/soil Nitrospira populations were analyzed. Meanwhile, their niche differentiation and associated environmental driving forces were characterized so as to predict their potential complete nitrification. [Results] Nine Nitrospira genera were detected, of which Nitrospira 1, 2 and 4 were dominated in xeric environment, which were negatively correlated with sand, water content, pH and ammonia nitrogen (AM) while positively correlated with nitrate nitrogen (NR), dissolved salt (DS), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), silt and clay contents. In comparison, Nitrospira 5, 6, 7, 8 and 9 were dominated in aquatic and hygric environments, positively correlated with sand content (except Nitrospira 9 negatively correlated with AM), etc. and negatively correlated with silt content, etc. Interestingly, Nitrospira 3 was preferentially distributed in the center of the river bed with aquatic environment, only positively correlated with sand and silt contents, but negatively correlated with the other environmental factors. [Conclusion] There was obvious niche differentiation of Nitrospira populations with a wide range of habitat adaptability in Xilin river basin. Nitrospira 1, 2 and 4 were most suitable to colonize xeric environment with relatively rich nutrients, positively driven by silt content, etc. Whereas Nitrospira 5, 6, 7, 8 and 9 were most suitable to inhabit relatively oligotrophic aquatic and hygric environments, positively driven by sand content, etc. Nitrospira 3 preferred silt, free water and low ammonia in oligotrophic aquatic environments, positively driven by only sand and silt contents. Briefly, silt content, dissolved salt (DS) and ammonia nitrogen (AM) were the main environmental driving forces for niche differentiation of Nitrospira groups. So i) Nitrospira 3 was presumed as probable comammox; ii) the other Nitrospira populations like 1, 2, 4, 5, 6, 7, 8 and 9 belong to comammox remains to be further discussed.

Key words:Xilin river basin, Nitrospira, Niche differentiation, Environmental driving forces, Comammox