Diversity Of Soil Bacterial Communities In The Eastern Margin Of The Taklimakan Desert

Taklimakan desert,located in the hinterland of Tarim Basin in Xinjiang,is the second largest mobile desert in the world.Desert is not a barren land,which contains abundant and diverse microbial resources.The special geographical location,arid natural environment and frequent wind sand activities make the wind sand landform of Taklimakan desert complex and diverse,and also provide a special living environment for microorganisms.The interaction between halophytes such as Populus euphratica,Tamarix ramosissima and karelinia caspica and microbial community constitutes a unique rhizosphere microbial community structure.In this study,21 samples of different types of sandy soil were collected from 10 different sampling points in the eastern edge of Taklimakan desert in June 2019,including 10 wind-blow sand samples,6 Tamarix ramosissima ledeb rhizosphere soil samples and 5 Populus euphratica rhizosphere soil samples.The structure of microbial community in different habitats in the eastern edge of Taklimakan desert was revealed by culture-free technology,and the relationship between community structure and environmental was revealed by the analysis of environmental factors;Actinomycetes were isolated from sandy soil samples by culture technique,and antagonistic strains of cotton verticillium wilt were screened;and a new suspected actinomycete species was polyphasic separated identification.The specific research results include:1.In this study,the total DNA of Desert sandy soil samples was extracted by suction filtration combined with SDS-CTAB method,and purification the DNA by kit.The high concentration and complete genomic DNA was obtained.By sequencing 21 sand samples collected from the eastern edge of Taklimakan desert,1 412 200 valid sequences were obtained,the OTUs of samples from different habitats were 22 730;the number of OTUs in the east edge of Taklimakan desert was much higher than that of other samples(Populus euphratica rhizosphere soil and Tamarix ramosissima ledeb rhizosphere soil)in the same habitat;the alpha diversity analysis of different sampling points in the eastern edge of Taklimakan Desert showed that,the OTUs of Washixia and Minfeng-Yutian were significantly higher than that of other samples(Populus euphratica rhizosphere soil and Tamarix ramosissima ledeb rhizosphere soil),Which meaned that,Washixia and Minfeng-Yutian have the highest microbial diversity and species abundance;Venn diagram and heat-map showed that sandy soil samples accounted for more OTUs then other samples,while the samples collected near the Qiala reservoir had the strongest specificity;By using UPGMA cluster analysis and NMDS analysis,We can found there was a certain similarity between microorganisms in each sampling area,and the same sample type could be clustered separately;through OTU species annotation,304 genera belonging to 42 classes of 21 phyla were identified from the 21 samples collected in the eastern margin of Taklimakan Desert,The dominant phyla were Bacteroidetes,Proteobacteria,Actinobacteria and Firmicutes;salinimicrobium have the highest relative abundance at the genus level,followed by Halomonas,sporophyta,Bacillus,Pontibacter,Aliifodinibius and Kocuria.Through the comparison of environmental factors,it is found that the differences of soil factors among the same sample types are extremely significant due to the changes of sampling areas.The difference of TP,SO₄^2-and HCO₃^-contents in the samples was the main driving force for the difference of microbial community.2.According to the information provided by the diversity of culture-free technology,G₂wind-blow sand sample was selected to isolation of actinobacteria,Which has the highest abundance of actinomycetes.natural air drying,dry heat treatment,wet heat treatment,phenol heat treatment,adding 0.05%SDS and 6%yeast extract,rehydration centrifugalization and ultrasonic treatment,were used to solation and purification of actinomycetes.Total of 209 actinomycetes were isolated according to 16S rRNA identification,they were Nocardiopsis,Micrococcus,Streptomyces,Isoptericola,Microbacterium,Kocuria,Amycolatopsis,Micromonospora,Pseudonocardia,Nonomuraea,Arthrobacte,Saccharopolyspor,Modestobacte and Gordonia in 7 orders and 10 families.209 strains of actinomycetes were screened for antibacterial activity.10 strains of actinomycetes had antibacterial activity against cotton fusarium wilt and 13 strains of actinomycetes had antibacterial activity against cotton verticillium wilt.3.Strain TRM 70200,a suspected new species of actinomycetes isolated from Taklimakan desert,was described by morphological characteristics,physiological and biochemical characteristics and molecular biological analysis.The results showed that TRM 70200 belonged to a new species of genus Pseudonocardia.In this study,high-throughput sequencing technology was used to describe the bacterial diversity and community composition in the eastern edge of the Taklimakan desert,and the relationship between environmental factors and microbial community composition was analyzed by culture-free technology;pure culture microbial technology was used to isolate and identify actinomycetes in the Taklimakan desert;and a new species of actinomycetes was identified,which provided reference for the subsequent exploration of microbial community in the Taklimakan desert.