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Lanzhou University (2010)

Diversity of Microrgansims Entrapped in the Tibetan Platean and Its Relation to Environment


Titre : Diversity of Microrgansims Entrapped in the Tibetan Platean and Its Relation to Environment

Auteur : 陈勇;

Grade : Doctoral Dissertation 2010

Université : Lanzhou University

Glaciers on the TIbetan Plateau contain a great deal of microogranisms with particular genetic characteristics due to the unique geological and environmental characteristics.Then the glaciers, therefore, become the nature huge repositories of viable microogranisms.The assemblages of airborne microorganisms immured chronolgically within glacier ice are species that were atmospheric constituents origianating from a variety of ecological scouces. So research on microogranisms of glacier on Tibetan Plateau is very important not only to stduy in extreme environments, but also to study how the microbe response the globe warmer change. This research would lead to the establishment of bio-indicator of gradual and repair climate change, and other physical phenonena.In this research, the bacteria were recovered from Dunde, Muztag ice cores and Qiangyong glacier from Tibetan Plateau by cultivation independent method and investigated by means of 16S rRNA sequence analysis.Their vertical quantiatitative changes were compared with the cariations in concentrations of mineral particles and oxygen isotope. The following major conclusions were obtained:1. Compare total cell count within three glaciers we can see the largest count occur in Dunde ice core. This result maybe has relationship with the climatic and surrounding of Dunde ice cap. This region locates the Qilian Mountain on the northersten margin of plateau.and the arid and semi-arid areas arround area. According to proxy record, dust storms was frequently than other two area. But the count of live cell from three glaciers is stable than total cell count show that speical speices such as some psychrophilic could grow in the ice core.2. The total cell count showed change along with depth of ice core,which corresponded to change of mineral particles andδ180 values. This study demonstrated that more bacteria accompanied with cold periods while less bacteria accompanied with warm periods at a large time scale. The further observation reflected the coincidence of abundant bacteria with rich micro-particles deposited in ice layer.3. In order to get a comprehensive picture of bacteria population diversity in Dunde and Muztag ice core, the bacteria DNA diversity were analyzed by 16S rDNA cloning library. Based on their 16S rDNA sequence,40.3%bacteria were Proteobacteria cluster,26%were HGC,24.9%were CFB in Dunde ice core. Whereas in Muzatg ice core,51.4%bacteria were Proteobacteria,24.9%were CFB and 24.9% were LGC. These differences suggested the evidence of the effect of climate and envirment on change of total bacteria.4. Based on 16S rRNA sequence, the determined sequences of the isolates in Dunde ice core were difference from the Muzatg ice core. All sequence wre similar to the sequence form other envirment such as soil, water and atmosphere. So the bacteria of ice core from the surrounding envirment of glacier. We also found the Shannon-Wiener index H’were 3.64 in Dunde ice core which was lower than 4.01 in Muzatg ice core. This result suggested that bacteria in Dunde ice core was more diversity than in Muztag which possibly due to its most complexity of ecosystem and diversity of biologic resource.5. Compare the sequence of four ice cores from the Muztag Ata Glacier (38 017’N,375 014’E,2006), Dunde ice cap (38 06’N,96024’E,2009), Puruogangri ice cap (33 044’N,34 004’E,89020’N,86050’E,2009), and Malan ice cap (33806’N,96 024’E,2004), respectively. The sequcence is similar with sequence from other cold envirment such as glacier and sea of polar. Which is due to strengthens the concept of adaptation and acclimation of microorganisms to the extremely cold glacier environments. Bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. This findings providepreliminary evidence of zone distribution of microbial community.which suggested the spatial and temporal biogeography of dominant bacteria across four geographically isolated glaciers.All research showed that bacteria compositions at different depths appear to be a reflection of the prevalent climate and individual events that occured at the time of deposition. We attempted to interpret the taxonomic diversity pattern of microorganisms across the mountain glaciers and provide information about possible driving forces of microbial community shift in glacier ice at a large spatial scale.

Mots clés : low temperature environment; glacier; 16S rRNA; phylogenetic diversity;

Présentation (CNKI)

Page publiée le 17 mai 2018