Microbial Diversity And Communitydistribution Characteristicsof The Soda Lakes In Badain Jaran Desert

There are numerous of lakes in Badain Jaran desert,which have a salinity gradient from freshwater to supersaturated lake and the soils around the soda lake also present the salinity variation,p H ranging from 8 to 11.Soda lake systems contained massive halophilic microorganisms,which played an important role in the ecological cycle of lakes.Therefore,we collected the water samples and soil samples from Badain Jaran desert,studied the ecological function of sulfate reducing bacteria in soda lake sulfur cycles,and analyzed the relationship between soil microbial community composition and environmental factors by the methods of molecular ecology such as clone library sequencing,Q-PCR and high-throughout sequencing in combination with Mothur,Canoco and R software.Meanwhile,some valuable halophilic bacteria were isolated.The main research results were as follows:(1)The species of sulfate-reducing bacteria in soda lake were rich and showed regular changes with salinity.The major genus of the freshwater lake was Desulfosarcina,the representative genus were Desulfobacterium,Desulfotignum in high saline lake,and Desulfohalophiluswas dominant in super high salt lake,which belong to extreme halophilic sulfate reducing bacteria.Most of these bacteria were anaerobic bacteria,some bacteria can participate in methane anaerobic oxidation process,and had an important impact in carbon and sulfur cycles.(2)The abundance of bacteria in soil samples was higher than that of in archaea,which percentages were 90.50%±0.17% and 9.50%±0.17%,respectively.Bacteroidetes(20.41%±0.12%)and Firmicutes(18.50%±0.12%)were the principal groups in soil samples,and distributed in each sample.Besides the two phyla,Gammaproteobacteria(8.53%±0.08%),Deltaproteobacteria(8.24%±0.04%)and Betaproteobacteria(5.45%±0.09%)were also the main members in middle and low salinity.In high salinity soils,Euryarchaeota(7.07%±0.14%)also was the representative phylum.(3)In low salinity soils the representative genus was Limnobacter,in middle and high salinity soils the representative genus were Thioalkalispira and Desulfonatronospira,and in super high salt solis the representative genus were Candidatus_Contubernalis and Halanaerobium.(4)Salinity affected the community composition of halophilic microorganisms in soils,and bacteria was the major group in the low salinity soils while the proportion of archaea was very low.But the proportion of archaea gradually increased with the salinity.However,salinity had no significant effect on ?-diversity,and Shannon diversity index could reach high value at high salinity or high p H environment.The soil microbial community structure was influenced by the combination of K+,Cl-,salinity,sulphate content and other environmental factors.(5)In this study,nine halophilic bacteria strains were isolated,and they belong to the genus of Bacillus,Halomonas,Salsuginibacillus,Salisediminibacterium,respectively,the optimum salinity of which was from 5% to14%.These strains were expected to play an important role in the field of high salt wastewater treatment.