The Microbial Diversity And Adaptive Characteristics In Saline Lake At Different Altitude Of Tibet Plateau

With the growing concern for environmental issues, the special geographical locationand species resources of Tibetan Plateau turn it into an ecological studing hotspot. As the firstaerogenic photosynthetic prokaryotes appeared on Earth, cyanobacteria becomes a modelorganism for scientific research as a result of its importance in ecological structure and uniquein the process of biological evolution. In this study, we took the saline lake at differentaltitude of Qinghai-Tibet Plateau as the research object and the microorganisms in these lakesas the research material, studied the relationship between the ecological factors and themicrobial diversity and adaptable characteristics of cyanobacteria in saline lake at differentaltitude of Qinghai-Tibet Plateau employing microbial isolated, purified and culturedtechniques, conventional microbiological classification techniques and molecular biologicalmethods. We obtained the unique microbial resources of saline lake at high altitude, andprovided a theoretical data for identifying and establishing microbial resources library, finallyachieved the following main findings:1. Using AB medium, we enriched cyanobacteria in Nam Co Lake, Yuncheng SalineLake and Qinghai Lake, which is at different altitude, and we isolated and purified11bacterial strains of cyanobacteria by capillary and agar plat method. Those strains wereGloeocapsa, Rhabdoderma, Dactylococcopsis, Microcystis, Oscillatoria, Chroococcus,Anabaena and Gomphosphaeria.2. Through expanding culture to isolated11cyanobacteria strains from Qinghai Lakeand Nam Co Lake we selected one strain of each above as research material, which waseugonic strain, while Microcystis of Yuncheng Saline Lake as a parallel control group. Afterlong-term UV-B radiation treatment, we studied the effect of long-term enhanced UV-B stresson the growth, metabolism, physiological activity and flexibility of cyanobacteria. The resultsshowed that,(1) Under UV-B stress, the content of biomass and soluble sugar of NMC1, QH4,YC1have demonstrated decline of varying degrees, but the range of decline of the highaltitude is much lower than YC1, and the changing trend is similar to each other. The contentof soluble sugar of QH4even exceeded its control group in the last day of treatment.(2)Under UV-B stress, unlike YC1, the content of chlorophyll a, phycobiliproteins andScytonemin of NMC1and QH4with the extension of the UV-B treatment showed the trendof delcine to upward basically.(3) Under UV-B stress, the content of Flavonoids ofcyanobacteria in high-altitude lake that NMC1and QH4showed that increased and thendecreased after prolonged treatment time, but the total was higher than the control groupwhich was YC1. The activity of CAT of the cyanobacteria QH4increased with increasingtreatment time, and the content of Flavonoids and the activity of SOD and CAT of YC1has showed a downward trend than the control group overall. Unlike cyanobacteria at low altitude,QH4and NMC1existed similar response mechanism and adaptability characteristics to thehigh-radiation environment, cyanobacteria at high-altitude lake withstanded the UV-Bdamage to cells preferably.3. We studied the microbial diversity of saline lake at different altitude taking theadvantage of metagenome sequencing technology. We mainly aimed at seasonal changes inmicrobial diversity of the Nam Co Lake, Yuncheng Saline Lake and Qinghai Lake in fivedifferent months, respectively, through the construction of clone libraries and on the part ofthe V4region of16S rDNA, then processed high-throughput sequencing and microbialdiversity analysis, and carried out a detailed analysis of research data, which includingdilution curve, diversity distribution curve, Venn intersection, Alpha diversity analysis, asingle sample of species distribution, RDA redundancy analysis.Then we had a conclusion that types of bacteria and the ratio of distribution of QinghaiLake and Nam Co Lake that had high similarity in dominant flora, mainly in Bacteroidetes,Proteobacteria, Actinobacteria and Verrucomicrobia. And those two lakes in June-Octoberperiod, the proportion of Planctomycetes mold would suddenly rise in common. The sort ofspecies abundance of these water samples was Q10>Y6>Q8>N10>N6>Q6>Y10>Q4>N5>N8>Y8>Q5>Y4>Y5>N4. The comparability extent of microbial species (genus) betweenNam Co Lake, Qinghai Lake and, Yuncheng Salt Lake were10.9%and18.4%respectively,while the comparability extent of microbial species (genus) between Nam Co Lake andQinghai Lake species reached more than37.6%, jointly owned by the three lakes accountedfor1,217species. Redundancy analysis combined with environmental factors showed that themicrobial diversity in Nam Co Lake was severely affected by light in June and Augustpositively, and air temperature and water temperature were closely related to the microbialdiversity of Yuncheng Saline Lake in June and October.