| The emergence and participation of life on the earth profoundly influenced and changed the evolution and historical process of the earth,forming the geosphere-biosphere-atmosphere.Biological processes,as active and powerful geological forces,play an important role in weathering,transportation,sedimentation and diagenesis of lithospheric materials,as well as in migration and enrichment of ore-forming elements,and have a profound impact on environmental changes and element cycle of the Earth's supergene system.With the progress of technology,the intersection of disciplines promotes the development of science and forms many comprehensive disciplines.In the field of geoscience,geomicrobiology is an interdisciplinary subject between Geoscience and biological science.It can comprehensively and systematically clarify the biogeochemical action and reveal the law of the change of the earth's environment.It has become a hot topic of international geoscience circles.Microorganisms complete the earth's element cycle through metabolic activities,and are closely related to many major environmental changes and geological and climatic events at global or local scales.In particular,extremophiles can not only help people to reveal the mysteries of the origin of the geosphere and biosphere,clarify the formation mechanism of biodiversity and the law of life evolution,but also provide new insights into global environmental change,and play a great role in environmental protection,climate change,resource development,human health,industrial biotechnology et al.In this study,aiming at microorganisms in different geological environment,such as mud volcanoes in Junggar Basin,sedimentary profiles in Linxia Basin in northeastern margin of Tibetan Plateau and acid pyrite leaching solution,we studied microbial community,metabolic pathway,diversity and interactions by using molecular techniques and bioinformatics analysis.The exploration of microbial geochemistry and its indicative role in environmental change has yielded the following achievements.1)Microbial community of mud volcanoes in Junggar Basin,XinjiangMud volcanoes are formed by the eruption and accumulation of underground mud and gas,and play a key role in the earth's carbon cycle.Taking two mud volcanoes(Dushanzi and Baiyanggou)in Junggar Basin of Xinjiang as research objects,the formation mechanism of mud volcanoes was explored according to their microbial composition analysis.The results showed that there were significant differences in bacterial community structure and archaeal community structure between Dushanzi and Baiyanggou.The diversity of bacterial community in Baiyanggou mud volcano was higher than that in Dushanzi,while the diversity of archaeal community was lower than that in Dushanzi.The Archaea found in Dushanzi mud volcano were anaerobic or extremely thermophilic,while those found in Baiyanggou mud volcano were halophilic,which were similar to the unique geographical characteristics of the two mud volcanoes.In addition,a large number of unidentified microorganisms were discovered in both mud volcanoes.The results of this study are of great importance not only to reveal the formation mechanism and origin of mud volcanoes,but also to provide a useful basis for oil and gas exploration in Junggar Basin in the future.2)Droughting of Microbial Records in Sediments of Maogou Section in Linxia Basin,Tibetan PlateauTaking the Cenozoic Maogou profile in Linxia Basin,northeastern margin of Tibetan Plateau as the research object,we utilized high-throughput sequencing and organic geochemical techniques to study the microbial community of sediment,and explore its action in climate change and indicative roles.The results show that the microbial communities in Maogou section at 26.47 Ma(30 m),14.04 Ma(204 m),8.03 Ma(314 m)and 5.41 Ma(398 m)were simple,the diversities were low,and the relative abundance of Firmicutes were high.On the contrary,the microbial communities in other depositional samples were complex in structure,high in diversity index,and Proteobacteria were abundance.Because Proteobacteria mostly prefers warm and humid environment and has poor resistance to stress,while Firmicutes is more adaptable to drought and extreme environment,it can be inferred that there were several drought events in the Cenozoic period of Maogou section sedimentary sequence at about 26 Ma,14 Ma,8 Ma and 5.4 Ma.3)Isolation,identification and functional analysis of acidophilic leaching microorganismsAcidophile can survive in acidic environment.They are of great significance to study the genesis of sulfide ores and their biogeochemical cycles of iron and sulfur in the earth.Molecular biotechnology,such as genome,macrogenome and transcriptome,was preferred to analyze the function of acidophile,and to explore the evolution law and biogeochemical role.Acidithiobacillus was the dominant species before and after domestication,but its proportion increased from 79%to 86.77%after domestication,and the proportion of Sulfobacillus in marginal species increased from 0.76%to 0.84%.After domestication,the functional genes of acidophilic leaching bacteria decreased,but their biological activities remained unchanged,and their functions evolved towards simplification.An extremely acidophilic bacterium hq2 was isolated from acidophilic leaching microflora 5Biol.The optimum growth temperature was 42? and the optimum pH was 2.Fe2+ could be oxidized to Fe3+.It could grow with yeast,but could not use other organic carbon sources such as glucose,sucrose,mannose,trehalose and malic acid.S0 and K2S4O6 could also be utilized.The ratio of GC was 52.44%.Genome analysis showed that the Calvin cycle and pentose phosphate pathway(PPP)in the basal metabolism of the strain were complete,but the glycolysis pathway(EMP)and tricarboxylic acid cycle were incomplete,and the nitrogen source could not be obtained by reducing nitrate/nitrite.No gene encoding Sox system was found in the sulfur metabolism pathway of hq2 strain,but genes encoding sulfur oxidoreductase(SOR)were found.It indicated that hq2 could grow with ferrous oxide,elemental sulfur and sulfide in the presence of organic substances.Additionally,the genome of strain hq2 contained complete flagellum synthesis genes,arsenic,copper and mercury resistance genes,which have good environmental adaptability and chemotaxis.It revealed that the isolate may be a newly discovered mixed-nutrient iron oxidizing bacteria,tentatively named Sulfobacillus sp.hq2.Two acidophilic bacteria,Sulfobacillus sp.hq2 and Acidithiobacillus sp.AC isolated from acidophilic leaching microflora 5Biol,were mixed cultured to establish a co-culture system to simulate the function of 5Biol.The results of comparative transcriptome analysis showed that Acidithiobacillus sp.AC gradually occupied the dominant position in the co-culture system after culture,which was consistent with the species proportion of 5 Biol.Sulfobacillus sp.hq2 not only activates the cell biological processes such as the synthesis of Acidithiobacillus sp.AC cell components and the function of protein,but also significantly promotes its growth.It also enhanced the ability of Acidithiobacillus sp.AC to oxidize sulfur and improved the iron oxidation ability of the co-culture system.Moreover,compared with pure cultures,genes of the sulfur metabolism and oxidative phosphorylation in Acidithiobacillus sp.AC were increased in the co-culture system,which enhanced the ability to store energy.Chemotaxis regulation genes and flagella synthesis genes were also significantly increased,indicating that bacterial chemotaxis was enhanced.Sulfobacillus sp.hq2 has a great influence on the global gene transcription of Acidithiobacillus sp.AC,which revealed at molecular level that the co-culture system of two bacteria has a stronger metabolic capacity. |
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