典型草原区不同生境反硝化菌群的空间特征

Spatial characteristics of denitrifying bacterial communities in different habitats from typical steppe

摘要:

【背景】锡林河-河滨湿地-阶地草原是蒙古高原典型草原区代表性的水生-湿生-陆生生境，但不同生境中反硝化菌群的空间分布特征尚不明晰。【目的】阐明典型草原区不同生境反硝化菌群的组成、丰度、空间分布特征及异质性成因。【方法】利用16S rRNA基因测序研究锡林河流域水生、湿生、陆生生境6个样带沉积物/土壤细菌群落组成及相对丰度。基于2014年及以前文献报道的反硝化细菌及16S rRNA基因信息构建参比菌库，筛选生境关联的反硝化菌属。通过典范对应分析等探究反硝化菌群空间异质性成因。【结果】参比菌库包含80种反硝化细菌(65个属)，6个样带测序获得的469个细菌属中36个为反硝化细菌属。3种生境共存的反硝化细菌有14个属，其中黄杆菌属(1.65%?14.17%)和噬氢菌属(1.56%?1.69%)是水生和湿生生境共有的优势菌，假单胞菌属(1.85%)是低河漫滩样带的优势菌。空间分布特征显示反硝化菌群沿水生-湿生-陆生生境呈现先升后降的分布趋势，在低河漫滩湿地达到最高值。典范对应分析表明：黄杆菌属、噬氢菌属、气单胞菌属、鞘氨醇单胞菌属等与pH值、水分及沙粒含量呈正相关关系，而芽孢杆菌属、链霉菌属、马杜拉放线菌属等与粘粒、粉粒、有机质、总氮含量等呈正相关关系。【结论】典型草原区反硝化菌群组成及丰度具有明显的生境异质性，低河漫滩湿地是反硝化细菌生长繁殖的最佳生境，由颗粒组成、水分含量和pH等环境因子共同驱动。

关键词:典型草原，代表生境，反硝化菌群，组成与丰度，空间特征，驱动力

Abstract:

[Background] Xilin river-riparian wetland-terrace grassland are the most representative aquatic-humid-terrestrial habitats in typical steppe region of Mongolia plateau, but little is known about the spatial characteristics of denitrifying bacterial communities in different habitats. [Objective] To reveal the composition, abundance, spatial distribution of denitrifying bacterial communities in different habitats of typical steppe region and associated spatial heterogeneity. [Methods] Using 454 pyrosequencing of 16S rRNA gene, we characterized community compositions and abundance of sediment/soil denitrifying bacterial communities from 6 sampling zones associated with aquatic, humid and terrestrial habitats. Based on the information of denitrifying bacterial 16S rRNA gene from previous references before 2014, we constructed denitrifying bacteria library as a reference to screen denitrifying bacterial genera associated with habitats. Meanwhile, we explored spatial heterogeneity of denitrifying bacterial genera by canonical correspondence analysis (CCA). [Results] The reference library contained 80 denitrifying bacterial species (65 genera). Accordingly, 36 denitrifying bacterial genera were screened out of total 469 bacterial genera from 6 sampling zones. Fourteen denitrifying bacterial genera co-existed in aquatic-humid-terrestrial habitats. Among them, Flavobacterium (1.65%?14.17%) and Hydrogenophaga (1.56%?1.69%) were dominant denitrifying bacteria across aquatic and humid habitats. Pseudomonas (1.85%) was the dominant bacteria only in low-floodplain wetland. The spatial distribution characteristics showed a tendency, first increased and then decreased along the aquatic-humid-terrestrial habitats, and reached peak value in low-floodplain wetland habitats. CCA analysis showed that Flavobacterium, Hydrogenophaga, Aeromonas and Sphingomonas were positively correlated with pH, water and sand contents. Whereas Bacillus, Streptomyces, Actinomadura were positively correlated with contents of clay, silt, organic matter and total nitrogen. [Conclusion] The compositions and abundance of denitrifying bacterial communities in typical steppe region showed obvious habitat heterogeneity. Low-floodplain wetland was the suitable habitat for growth and reproduction of denitrifying bacteria, which were driven by multiple environmental factors such as sediment/soil particle compositions, water content and pH.

Key words:Typical steppe, Representative habitats, Denitrifying bacterial communities, Composition and abundance, Spatial characteristics, Driving force