Community Structure Analysis Nitrate Dissimilation Reduction To Ammonium In Typical Farmland Soil

N2 gas is the most abundant gas in the earth’s atmosphere.It is extremely inactive and is not easy to react with other substances to form new compounds.Nitrogen fixation is the process of transforming N2 in the earth’s atmosphere into ammonia or other molecules that can be used by organisms.Biological nitrogen fixation is a microbial process that transforms N2 into plant usable form.As an inorganic fertilizer substitute,BNF is considered as an important source of soil nitrogen input.Because nitrogen is an essential nutrient for all organisms,the lack of fixed nitrogen will limit the productivity of ecosystem,so N2 fixation is the key process of nitrogen cycle.In this paper,the corn field soil near Songhua River in Harbin city is taken as the main research object.The community structure,diversity,internal connection and occurrence law of bacteria reducing nitrate to ammonium by dissimilation are studied by combining traditional biological methods,new generation high flux technology,Ecological Grid Analysis and statistics.The microbial community structure of rhizosphere and non rhizosphere soil was analyzed in summer and winter respectively,and the distribution and occurrence of nitrate reducing microorganisms in different depths of soil were studied.In order to complete the coupling reaction mechanism of nitrate dissimilation reduction reaction,the community structure of related nitrogen cycle processes such as anaerobic ammonia oxidation and denitrifying bacteria was extended.The community composition of nitrate dissimilation reduction to ammonium process(DNRA)was analyzed by high-throughput sequencing of NrfA,the functional gene of DNRA.DNRA bacteria are divided into 25 different genera according to genus genus.Among them,anaeromyxocharacter,sorangium and hyalangium accounted for 21.84%,17.78%and 15.94%respectively.Anaeromxobacter is the key bacterium of DNRA,which plays a leading role in the process of DNRA through network analysis and high-throughput data analysis.Through the network analysis and high throughput analysis of ANAMMOX,it is shown that Candidatus brocadia sp.is the dominant bacteria in anammox process.Bradyrhizobium and Mesorhizobium are the dominant genera of denitrifying microorganisms,with high abundance and strongest connection with other genera.DNRA,anammox and denitrification complement each other in the population structure and the potential mechanism of the coupling reaction.The three reactions are greatly affected by environmental factors.Through PCoA analysis(OTUs level)and cluster analysis,it shows that seasonal difference is the key to the difference between samples.However,root system and non root system had little effect on the community structure of nitrogen cycling microorganisms.Environmental factors C and N are important environmental factors that affect the dissimilation reduction and denitrification of nitrate.This study explored the role of DNRA bacteria in the environment,the significance of new nitrogen cycle and the application value of soil nitrogen retention.It is of great significance to comprehensively study the ecological function of farmland microorganism and analyze the microbial community structure in the process of farmland nitrogen metabolism.By comparing the differences of microbial ecology and microbial community structure among sample points,not only the evolution mode of farmland microorganism can be understood,but also the role of plant decomposing in Biogeochemistry can be realized Therefore,it is of great significance to study the consolidation of ammonium in farmland soil,the maximum application of nitrogen by plants,and the new nitrogen cycle and soil nitrogen retention.