Temporal And Spatial Distribution Pattern Of Rhizosphere Nitrogen-fixing Microorganisms In The Ebinur Lake Wetland And Isolation And Identification Of Myxobacteria

[Objective] The primary goal of this study was to explore the correlation between the diversity and abundance of nitrogen-fixing microbes and the physic-chemical factors of rhizosphere and non-rhizosphere soil types during different seasons in four Vegetation community of Ebinur Lake wetland.We aimed to explore the potential role of nitrogen-fixing microbial communities in restoring ecological functions.This study may provide the theoretical foundation and preliminary data for future studies in this field.It is the first attempt to isolate and identify myxobacteria in Ebinur Lake wetland by different methods.In order to enrich the database of myxobacteria in arid areas of China,to find a more concise and efficient method of isolation and purification through compare the advantages and disadvantages of different methods,and make a good foundation for the future work.[Methods] In this paper,the rhizosphere and non-rhizosphere soils of Halocnermum strobilaceum,Salicornia europaea,Kareliniacaspia and Reed were collected from the Ebinur Lake wetland in July,October and April.The dynamic changes of soil environment in Ebinur Lake wetland were studied by measuring soil physic-chemical factors at different times.Illumina HiSeq PE250 sequencing technique was used to analyze the diversity of nitrogen-fixing microorganisms in six different soil samples.RDA analysis was used to explore the correlation between the physicochemical factors and the structure and abundance of nitrogen-fixing microbial communities in these soil samples.Bacteriophilic myxobacteria were isolated by Escherichia coli marking method and rabbit feces induction method.The identified of myxobacteria were by colony morphology observation,molecular sequencing and physiological and biochemical identification.[Result] Soil physic-chemical factors showed that pH was 7.42-8.97 with an average of 7.83,alkalization degree of Ebinur Lake wetland soils was July > April > October,all of which were alkaline soils.The water content ranged from 4.30% to 14.38% with an average of 8.62%,the change of soil water content in each month was April > July > October,and the water content was lower than the normal wetland level.The conductivity ranged from 0.16 ms/cm to 12.40 ms/cm,with an average of 4.68 ms/cm.The seasonal variation of soil salt content was July > October > April,and the salt content of rhizosphere soil was higher than non-rhizosphere soils.The soil of OM,SM,EC,TK,AN,AK,AP contents showed significant differences in different periods.Diversity analysis showed that Chao1 index,ACE index and Shannon-Wiener index of nifH gene in rhizosphere soil of Ebinur Lake wetland were higher than those in non-rhizosphere soil.Cluster analysis of TOP100 genus showed that soil nitrogen-fixing microorganisms in Ebinur Lake wetland belonged to eight nitrogen-fixing bacteria phylum,namely Proteobacteria,Cyanobacteria,Firmicutes,Spirochaetes,Euryarchaeota,Actinobacteria,Chlorobi and Thermodesulfobacteria.Among them,Proteobacteria is the first dominant group of nitrogen-fixing microorganisms in Ebinur Lake wetland.Geobacter,Pseudomonas and Bradyrhizobium are dominant bacteria in different samples of Ebinur Lake wetland.The dominant nitrogen fixing bacteria were different in rhizosphere soil and non-rhizosphere soil of Ebinur Lake wetland in July,October and April.RDA analysis showed that AK,TP,TN and AN was significantly correlated with the diversity and richness of nitrogen-fixing microorganisms.In the experiment of isolation and identification of bacteriophilic myxobacteria in Ebinur Lake wetland,there were two strains of myxobacteria YJC9 and HHC2 obtained by E.coli marking method.The strains YJC9 and HHC2 were classified as Myxococcus by morphological observation,molecular identification,physiological and biochemical reaction.[Conclusion] The sois were saline-alkaline soil with low water content and low evaluation of soil nutrient grade.The diversity of nitrogen-fixing microorganisms in rhizosphere of soil samples was higher than that in non-rhizosphere soil samples,and that in July was higher than that in October and April.The diversity and community structure of nitrogen-fixing microorganisms in soil may be affected by conductivity,water content and alkali-hydrolyzed nitrogen.The content is less of bacteriophilic myxobacteria in the saline-alkali land of the Ebinur Lake wetland.