锡林河流域潜在不产氧光合细菌陆向分异特征及影响因素

Landward differentiation characteristics of anoxygenic photosynthetic bacterial populations and their influencing factors in Xilin River Basin

摘要:

【目的】为探明锡林河流域潜在不产氧光合细菌(anoxygenic photosynthetic bacteria，AnPB)的陆向分异特征及影响因素。【方法】本研究沿着陆向梯度依次采集水生湍流带、缓流带、滞流带、水偏湿生样带、湿偏旱生样带、旱生样带土壤样品。基于文献建立AnPB在科水平的数据库，运用16S rRNA基因高通量测序筛选科水平潜在AnPB类群及其组成丰度的陆向分异，运用皮尔逊相关性及冗余分析等研究土壤理化因子对潜在AnPB陆向分异的影响。【结果】紫色硫细菌(外硫红螺菌科)和紫色非硫细菌(红杆菌科、红环菌科、醋酸杆菌科、丛毛单胞菌科、全噬菌科)主要分布在水生及水偏湿生生境，其相对丰度与湿度呈显著(P<0.05)或极显著(P<0.01)正相关关系；紫色非硫细菌(红螺菌科、慢生根瘤菌科、生丝微菌科、红菌科)、芽单胞菌科、酸杆菌科、绿色非硫细菌(蔷薇菌科)等主要分布在湿偏旱生和旱生环境中，其相对丰度与盐度和全氮含量呈显著(P<0.05)或极显著(P<0.01)正相关关系；多元回归树分析显示，盐度、湿度、全氮对潜在AnPB陆向分异的总解释度分别为62.39%、14.01%、12.68%；结构方程模型拟合结果显示，盐度对红环菌科及全氮和湿度对红杆菌科均发挥正向直接作用。【结论】锡林河流域潜在AnPB具有明显的陆向分异规律，盐度、湿度、全氮是直接或间接驱动潜在AnPB陆向分异的主要环境因子。【意义】该研究结果有助于加深对锡林河流域AnPB生物多样性与生态系统功能的认识，为减少大气中CO₂排放和增加土壤固碳提供科学依据。

Abstract:

[Objective] This study aimed to elucidate the landward differentiation characteristics of potential anoxygenic photosynthetic bacteria (AnPB) and their influencing factors in Xilin River Basin. [Methods] Soil samples were collected along a landward gradient from the turbulent flow zone with no plant (Np), sluggish flow zone with Juncellus serotinus (Js) and stagnant flow zone with bacterioplankton (Pb) in riverbed, the riparian zones including semi-aquatic (hygrophytic) Juncus effusus (Je) and semi-xerophytic (hygrophytic) Potentilla anserina (Pa) to terrace zones including xerophytic Leymus chinensis (Lc) and Stipa grandis (Sg). The database for AnPB at family level wasestablished based on literature informatics. In addition, landward differentiation of potential AnPB populations at family level and their relative abundance was analyzed by 16S rRNA gene high-throughput sequencing. Furthermore, the environmental influence of physicochemical factors on landward differentiation of potential AnPB was studied based on Pearson correlation analysis, redundancy analysis (RDA), multivariate regression tree (MRT) and structural equation modeling (SEM). [Results]Purple sulfur bacteria (Ectothiorhodospiraceae) and purple non-sulfur bacteria (Rhodobacteraceae, Rhodocyclaceae,Acetobacteraceae, Comamonadaceae and Holophagaceae) populations were mainly distributed in aquatic and semi-aquatic (hygrophytic) habitats, whereas purple non-sulfur bacteria (Rhodospirillaceae, Bradyrhizobiaceae, Hyphomicrobiaceae and Rhodobiaceae), Gemmatimonadaceae, Acidobacteriaceae and green non-sulfur bacteria (Roseiflexaceae) populations were mainly distributed in semi-xerophytic (hygrophytic) and xerophytic habitats. Herein, the relative abundance of the potential AnPB populations in aquatic and semi-aquatic (hygrophytic) habitats showed positive correlation with moisture content (P<0.05 or P<0.01), while that in semi-xerophytic (hygrophytic) and xerophytic habitats was positively correlated with salinity and total nitrogen content (P<0.05 or P<0.01). MRT analysis indicated that the total explanation of salinity, moisture and total nitrogen for the landward differentiation of the potential AnPB populations was 62.39%, 14.01%, and 12.68%, respectively. SEM revealed the positively direct links between salinity and Rhodocyclaceae as well as between moisture/TN and Rhodobacteraceae. [Conclusion] The landward differentiation of potential AnPB populations in Xilin River Basin is clear. Salinity, moisture and total nitrogen are main environmental factors directly or indirectly co-driving the landward differentiation. This study contributes to a better understanding of the biodiversity and ecosystem function of AnPB community in Xilin River Basin, and also underpins the implementation of an innovative strategy for reducing atmospheric carbon dioxide concentration and increasing soil carbon sequestration.