Microbial Ecology And Nitrogen Cycle Metagenomic Analysis In Aquifers And Soil Layers

Groundwater is a valuable freshwater resource on Earth and is the drinking water resource in many countries.However,the ecological balance of groundwater has been seriously undermined by long-term overexploitation of groundwater and unreasonable disposal of domestic wastes and industrial wastes.At present,the investigation of microbial community and nitrogen cycle process in groundwater aquifers and soil layers mainly is focused on single soil type,single pollutants or single nitrogen cycle process,which could not reveal the microbial geochemical cycle in groundwater aquifers and soil layers ecosystem simultaneously and comprehensively and clarity the influence of environmental factors on microbial community,each nitrogen cycle process and the interaction among each nitrogen cycle process.In this study,microbial ecology and nitrogen cycle macrofactor groups in groundwater aquifers and soil layers in different regions(Antu,Baiyangdian,Jilin,Bremen,Zurich and Queensland)and seasons(spring,summer,autumn and winter)were studied by sequencing technology of metagenomic bird-gun method and bioinformatics analysis method.The results were as follows:(1)The microorganisms driving biogeochemical cycles in aquifers and soil layers are mainly bacteria.Proteobacteria and Actinobacteria dominate at the phylum level.The second is archaea.Thaumarchaeota and Euryarchaeota are the dominant microorganisms which have some competitive relationship.Each sample site has its own unique composition of microbial species.(2)The microbial diversities in aquifers and soil layers are rich and stable.The stability of aquifer is higher than that of soil layers.The stability of spring and summer is higher than that in winter and autumn.The microbial community composition and functional composition structure are similar except for Zurich.The diversities of functional genes in spring and summer are more stable than those in autumn and winter.The differences in diversity of functional genes,metabolic pathways,community composition and functional composition were small.(3)The nxr A gene,nar G gene and nxr B gene are the most abundant gene of nitrogen cycle processes in aquifers and soil layers which are hardly affected by environmental factors.NO₃^-and NO₂^-drive the nitrogen cycle in aquifers and soil layers.(4)The nitrogen cycle in aquifers and soil ecosystems is dominated by denitrification and dissimilatory nitrate reduction to ammonium,followed by complete ammonia oxidizing.In the aquifer system,denitrification and dissimilatory nitrate reduction to ammonium are stronger in summer than in winter.In the soil system,comammox and assimilatory nitrate reduction to ammonium are stronger in spring than in autumn.Nitrogen fixation,denitrification and assimilatory nitrate reduction to ammonium are stronger in summer than in winter.