干湿交替对生物滞留系统中氮素功能微生物群落的影响

【目的】为探究生物滞留系统干湿交替下环境因子对氮素功能微生物群落的影响。【方法】应用高通量测序技术(Illumina MiSeq PE300),并以amoA和nirS功能基因为分子标记,对无植物型和植物型生物滞留系统在干湿交替下不同土壤空间位置(种植层、淹没层)的硝化和反硝化细菌的多样性和群落结构进行研究,并对微生物群落与环境因子的相互关系进行相关性分析。【结果】微生物种群的功能基因存在显著的空间差异,相比淹没层,种植层的功能细菌更丰富。种植层的OTUs高于淹没层,而进水再湿润促使两种功能基因在种植层和淹没层的OTUs占比差异性增大。群落组成分析表明,amoA型硝化细菌和nirS型反硝化细菌的优势细菌门均为变形菌门(Proteobacteria)。虽然植物根系对氮素功能微生物的多样性指数影响不显著,但在属水平上,植物系统种植层的反硝化菌群种类高于淹没层,而无植物系统则刚好相反。CCA/RDA分析表明,土壤空间位置是影响硝化和反硝化菌群结构的最重要环境因子。【结论】本研究证实干湿交替运行下生物滞留系统中的氮素功能微生物群落受土壤空间位置、水分含量和植物根系的共同调控,其机制有待进一步研究。

Effects of drying-rewetting alternating on nitrogen-related microbial functional communities in bioretention systems

Objective] This study aims to explore the effect of environmental factors on nitrogen-related microbial functional community structure of bioretention systems under the condition of drying-rewetting alternation.Methods] Soil samples were collected from spatial distribution (planting layer, submerged layer) in vegetated and un-vegetated bioretention systems after drying and rewetting. The amoA and nirS functional genes were used as molecular marker. The diversity and community structure of nitrifying and denitrifying bacteria in different soil samples were studied by high-throughput sequencing technology named Illumina MiSeq PE300. Canonical correlation analysis (CCA) and redundancy analysis (RDA) were performed to assess the relationship between nitrogen-related microbial functional community structure and environmental factors was analyzed.Results] The functional genes of microbial populations showed significant spatial differences. Nitrogen-related functional bacteria in the planting layer were more abundant and diverse than which in the submerged layer. However, the differences in proportion of operational taxonomic units (OTUs) between the two functional genes in planting layer and submerged layer were increased by rewetting. The results from the community composition analysis of nitrogen-related functional microbes showed that the dominant phylum of amoA-nitrifying and nirS-denitrifying bacteria were the Proteobacteria in all the soil samples. The root system of plants had no significant effect on the diversity index of nitrogen-related functional microbes, but in the plant system layer, the denitrifying bacteria species (at the genus level) were more than that in the submerged layer, and the opposite trend were showed in the plant-free system. The analysis of CCA and RDA showed that soil spatial distribution was the most important environmental factor on the distribution of nitrifying and denitrifying microbial communities.Conclusion] The nitrogen-related functional microbial community in bioretention system under drying and rewetting alternation was controlled by the soil spatial distribution, water content and plant roots. However, the underlying reasons still await further investigation.