【作者】 陈勇；

【导师】 安黎哲；

【作者基本信息】 兰州大学 ， 植物学， 2010， 博士

【摘要】 冰川由于其独特的地理环境特征蕴藏着大量具有独特遗传学和适应环境变化机制的微生物,是一个天然的微生物的“储存库”,记录着不同时期大气环流向冰川输送的微生物菌群数量和结构变化,是包含生物进化以及地球上生物生存环境变化信息的优良介质。所以研究冰川中的微生物不仅是极端环境下生物生态研究的重点,也是研究全球气候变暖背景下微生物对气候环境变化响应的重要方面。本研究应用先进的流式细胞技术和建立16S rRNA基因文库的方法以敦德冰芯,慕士塔格冰芯以及西藏枪勇冰川现代雪冰为介质,分析和讨论了我国青藏高原冰川细菌菌群数量和结构变化的特征及其与气候环境的关系,菌群的地理学分布特征以及与微粒和氧同位素代用指标的关系,并获得了以下主要结果：1.不同大气环流影响造成了冰川生物量不同。应用先进的流式细胞技术测定发现细菌总数以敦德冰芯数量最多,枪勇冰川次之,慕士塔格冰芯数量最少。这可能是因为青藏高原北部慕士塔格和敦德冰川受到西风环流的影响而南部枪勇冰川主要受印度洋的暖湿气流影响,位于青藏高原最西端祁连山的敦德冰川相比其他冰川更加干旱,周围被沙漠和戈壁包围的地理环境特征。但是活细菌的数量在三个冰川中的变化则不大,说明同样极端冷的微环境使特定的一些适应冷环境的菌群能够保持一定的活力,具有相对稳定的数量。2.冰川细菌数量的变化是气候环境变化的指示。菌群数量随冰芯深度呈波动性的变化,与微粒数量波动性的变化基本一致,在污化层对应的冰层中有着相对更多的细菌,说明冰川中的细菌与大气中的尘埃有密切联系。从δ180随深度的变化曲线分析,记录到的峰值所对应的时期与细菌以及微粒含量较高的时期是基本对应的,说明冰川中细菌的分布具有明显的季节性分布现象,揭示了冷干期微粒和细菌数量高暖湿期数目低与大气温度负相关的对应关系。冷期强劲风不仅为冰川输送了大量粉尘微粒,也带来了大量的细菌源。但这也并非是一一对应的关系,在一些微粒含量较低的冰层也发现了较高的细菌数量,这也提示了冰川中的细菌并非只来源于尘埃颗粒,还可以是通过高空气溶胶和水蒸气输送等方式进入冰川。3.分析冰川细菌16S rRNA基因文库发现,敦德冰芯中所有克隆到的16SrRNA序列代表的原核生物形成的类群以及优势菌群与慕士塔格冰芯有很大不同。说明不同地理气候环境冰川对细菌类群的组成有重要影响。这些菌群与在土壤、湖水、大气溶胶中发现的菌属有很高的相似度,提示冰川中的细菌主要来源于周围环境的输送。4.冰川细菌菌群的结构和多样性反映了气候环境变化特征。从各类群在冰芯剖面上的分布状况分析来看,敦德冰芯细菌菌群中,以Proteobacteria, HGC以及CFB为主要组成部分,分别占到40.3%,26%和24.9%,而在慕士塔格冰芯中Proteobacteria(51.4%), CFB(20.2%)和LGC(20.2%)为主要组成部分。这种分布的差异特征都反映了不同时期的气候变化对于细菌菌群在冰川中分布的影响。慕士塔格冰芯中细菌多样性指数(H)最高达到4.01,而敦德冰芯中H值最高仅为3.64,说明了慕士塔格冰芯中细菌类群有着更好的多样性,这可能与该冰川生态系统的复杂化以及生物资源的多样性有关。5.通过四个不同位置的冰川基于16S rRNA序列对比分析发现,冰川中的细菌种类与从极地的冰川、海冰、以及其他冷环境中分离的细菌有很高的相似度,遗传距离很近,这是相似的冷环境对于细菌类群的选择性以及这些菌群对环境的适应性长期进化的结果。同一冰川中细菌16S rRNA序列具有很近的遗传距离,集中聚合在一起,而与其他不同位置冰川中的细菌16S rRNA序列遗传距离较远,尤其体现在优势菌属中。可能是因为不同地理环境位置的冰川对细菌长期的进化选择造成的。同时还发现根据冰芯深度的不同,广泛分布种属在不同层面冰芯中的比例不同,证明了细菌类群具有季节性分布的特点。这说明,冰川中细菌种群具有区域分布的特点,细菌类群生物地理分布具有时空特征。以上研究都揭示了气候环境变化对于冰川细菌的数量以及种类分布具有重要的影响,菌群组成结构的变化是气候环境变化的响应,长期环境的选择使冰川细菌具有生物地理划分区域的特点。为冰川细菌多样性的分类模式以及不同环境下菌群类别发生变化可能的影响因素做了有益探讨。更多还原

【Abstract】 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.更多还原