Diversity Of Bacteria And Archaea In The Sediments Of Longfeng And Dangnai Wetland And Expression Of Denitrifying Gene

With the development of urbanization,the wetland environment in the urban area is seriously affected by human activities.However,there is no unified conclusion on the differences of physical and chemical parameters,microbial diversity and gene expression of nitrogen cycle related functions of wetland sediment disturbed by human activities in different seasons and the response relationship between them.Therefore,in order to explore the response between microbial community changes and human disturbance in natural wetlands in different seasons.The sediment samples of Longfeng wetland(urban wetland)and Dangnai wetland(natural wetland)were collected respectively to determine the physical and chemical parameters of the sediment.The community composition of bacteria and archaea in the sediment was determined by 16 S r RNA gene sequencing technology.The expression of denitration gene nir S,nir K gene and assimilation nitrate reduction gene nir A in the wetland sediment was determined by fluorescence quantitative PCR.Combined with Spearman correlation analysis,To explore the response of bacterial and archaeal community composition to the differential expression of physical and chemical parameters of wetland sediment and functional genes related to nitrogen cycle.So as to reveal the response law of wetland sediment microbial community structure to human disturbance,in order to find the microbial community that has changed significantly after human disturbance,and provide a theoretical basis for preventing wetland degradation and other environmental problems caused by wetland disturbance.The main results are as follows:1.Longfeng wetland is affected by urban human activities.The p H value,salinity,cation exchange capacity and total organic matter content of sediment are lower than those of funai wetland.There is a significant difference in cation exchange capacity and total organic matter content between the two wetlands(P < 0.05),while the contents of total carbon,total nitrogen,total phosphorus and ammonium nitrogen and protease activity are higher than those of Dangnai wetland.There is a significant difference in ammonium nitrogen content and protease activity between the two wetlands(P < 0.05).Alkaline phosphatase,sucrase and urease activities showed no significant difference between the two wetlands.2.Proteobacteria is the dominant bacterial phylum shared by Longfeng wetland and Dangnai wetland,and the dominant bacterial genus is uncultured＿bacterium＿f＿Anaerolineaceae.In Longfeng wetland,the relative abundance of Thiobacillus,Bacillus and Sphingomonas was significantly higher than that in Dangnai wetland(P< 0.05).The dominant archaea in the two wetlands is Euryarchaeota,and the dominant archaea genus is uncultured＿bacterium＿c＿bathyarchaea and methanoregula in the sediment of Dangnai wetland was higher than that of Longfeng wetland in both seasons,and the difference was not significant.3.The expression levels of denitrifying genes nir K and nir S in the sediment of Dangnai wetland in winter were significantly higher than those in Longfeng wetland in winter,Longfeng wetland in summer and Dangnai wetland in summer(P < 0.05);The expression of nitrate assimilation reduction gene nir A was the lowest in Longfeng wetland in summer,which was significantly lower than that of the other three groups(P < 0.05).4.Nitrate nitrogen content is the most significant environmental parameter affecting the species composition of microorganisms and the expression of nitrogen cycle function genes in this study.Human disturbance reduces the p H value,salinity,cation exchange capacity and total organic matter content of the wetland,and the buffer capacity of the wetland.The relative abundance of Thiobacillus,bacillus and Sphingomonas in the disturbed Longfeng wetland sediment is significantly higher than that in Dangai wetland,which can be used to speculate whether the wetland is disturbed.The relative abundance of methanoregula is higher in the undisturbed Dangnai wetland,which can be used as an indicator of whether the natural wetland is disturbed or not;The expression of denitrifying genes nir K and nir S was the highest in Dangnai wetland in winter.Chloroflexi was the main denitrifying group in this study,and Verrucomicrobia was the main bacterial group assimilating nitrate gene nir A in this study;Nitrate nitrogen content is the main driving factor of microbial community change after wetland disturbance in this study.