Study On Soil Bacterial Community Diversity Between Different Habitats Of Mud Volcanoes In Xinjiang

Mud volcano, which is the largest volcano in the Usu region of Xinjiang in Asia, has typical geological structure, special climatic environment and provide uncommon environmental conditions for unique microbial resources. Taking mud volcano as reference, we selected typically four different soil habitats to take samples in April, July and November, 2014, and the four different habitats were named as A, B, C, D, respectively. We set plots based on 5-point sampling method in different habitats and collected soil samples, then measured soil physical and chemical properties(water content, pH, conductivity, organic matter, total nitrogen, total phosphorus, total potassium) and soil enzyme activities(catalase, invertase, urease, phosphatase), we researched spatial dynamic change of soil bacterial community and selected dominant strains by using traditional culture methods. Besides, we analyzed the correlation between soil physical and chemical properties, soil enzyme activities and the number of soil bacteria, we also combined with Illumina Miseq sequencing methods to further study on soil bacterial community diversity between different habitats of Mud Volcanoes in Xinjiang. These will lay the theoretical foundation for research of mud volcanoes ecosystems research comprehensively and provide guidance for rational exploitation of microbial resources in mud volcanoes.In traditional culture methods, the number of bacteria was most abundant amount of up to 7.8×105cfu/g in April by using dilution-plate method, and through morphological identification, 24 strains bacteria were screened out initially and then we stu died their biological characteristics of the 24 strains by the liquid shake culturing and measuring the turbidity, the optimum temperature, optimum pH and growth curve were obtained for each of the 24 strains. On the basis of that, we studied the physiological and biochemical characteristics of every strain by using molecular identification of bacteria 16 S rRNA method, then we analyzed the phylogeny of microorganism. The 24 strains were mainly divided into three categories, namely the Firmicutes, Actinobacteria and Proteobacteria for 13 genus. 5 strains were vested in Bacillus, 5 strains were vested in Pseudomonas, each 2 strains were vested in micrococcus, Paraoccus, Kocuria, each 1 strain was vested in Paenibacillus, Chryseobacterium, Isoptericola, Flavobacterium, Sinorhizobium, Ornithinimicrobium, Terribacillus, Pontibacter. The dominant bacteria were Bacillus and Pseudomonas in Usu mud volcanoes.Through soil physical and chemical properties analysis, the results revealed that water content, organic matter, total nitrogen, total phosphorus, total potassium of type C(except pH, conductivity) had the highest content in soil habitats. Type D has lower content in total nitrogen, total phosphorus, total potassium. From the season aspects, soil physical and chemical properties’ s change presented different trends with the season. Through the enzyme activities analysis, sucrose, urease, phosphatase(except catalase) had significant differences as the seasons change(P<0.05). Catalase activity and urease activity was highest in type D, invertase activity and phosphatase activity was highest in type A. Through correlation analysis of soil physical and chemical properties, soil enzyme activity and the number of culturable bacterial communities, the results showed that the number of bacterial communities and organic matters, total nitrogen had a extremly significant positive correlation( P<0.01), and catalase activity and urease activity have a significant positive correlation( P<0.05). In conclusion, soil nutrients can have an impact on soil fertility by participating in the nitrogen cycle in soil, thereby affecting soil enzyme activities and the number of soil bacteria, that is, the number of soil bacteria were influenced by soil nutrients and soil fertility.Combined with Illumina Miseq sequencing, we further analyzed soil bacterial community diversity of mud volcanoes in Xinjiang Usu, the results showed that a total number of 29005 operational taxonomic units(OTUs) were obtained from mud volcano soil under the similarity level of 97%. For phyla level, we had got 38 groups of bacterial that the Proteobacteria, Actinobacteria and Bacteroidetes were the dominant groups; For class level, we had got 46 grouds, Gammaproteobacteria was the most important subdivision in Proteobacteria; For genus level, we had got 72 groups, but the most abundant genera was unclassified. Diversity index revealed that the type D had a higher abundance effect and diversity index. Compared with the bacteria community diversity and physicochemical property, we found that bacteria diversity was decreased as the increase of soil fertility, which shows negative correlations between bacteria diversity and physicochemical property. The results of PCA and heat map indicated that the community composition of type A has no significant variation with space-time dynamic changes, but type C is opposite.