【作者】 林娟；

【导师】 徐世健； 张新芳；

【作者基本信息】 兰州大学 ， 植物学， 2009， 硕士

【摘要】 冰川是微生物的储存库,为研究不同历史时期环境条件对生物多样性时空变化的影响以及丰富物种多样性提供了极好的框架。微生物在沉降过程中的变化,不仅受到沉积时气候环境的影响,也受到沉积后微生物的生长、降解、溶水冲刷和雪→冰环境改变的影响。本研究对天山1号冰川PGPI点4月（snow pit-1）和5月（snow pit-2）所挖的两个雪坑和钻取的一段浅冰芯不同深度样品中的微生物数量和多样性进行了研究,分析了微生物与环境之间的关系,主要得出了如下结论:雪坑中微生物总数为0.7×10³-2.16×10⁵ cells·mL^-1,可培养细菌数为0-550cfu·mL^-1,snow pit-2细菌总数平均值为snow pit-1的1.5倍,但可培养细菌数却为7.5倍,这种大的差异可能是5月的环境更利于细菌的生长繁殖和复苏。两个雪坑中微生物数量出现高值区和低值区,它可能是两个季节的旋回,春夏季时微生物数量出现峰值而秋冬季出现低值与大气气流和来源地密切相关。天山1号冰川浅冰芯中微生物总量为1.4×10³-1.0×10⁵ cells·mL^-1,可培养细菌数量为0-300cfu·mL^-1,冰片中微生物总量和可培养细菌的数量较多,粒雪层中相对少的多,这可能是雪层中的微生物及粉尘颗粒随融水的淋溶作用进入冰层。冰片中微生物总数和可培养细菌数量随深度呈递减的趋势,可能是近几年环境变化或人类活动频繁使大气中携带更多的细菌和颗粒物质沉积在冰川上,也可能是细菌发生自溶或被降解所致,还有待进一步研究证实。微生物总数与可培养细菌之间也有一定的对应关系,但并不是一一对应,说明除了来源和繁殖因素外,细菌种类组成也影响着可培养细菌的数量。分离到的天山1号冰川雪坑的24株可培养细菌分属于4大类的18个属,其中Actinobacteria中属的种类最多,CFB类、Actinobacteria、Firmicutes类这三大类是可培养细菌的主要类群,Proteobacteria极少,4、5月所挖雪坑样品中,CFB类所占比例分别为53.5%和54%,Actinobacteria所占比例分别为26%和28.5%,Firmicutes类所占比例分别为14%和12%,Proteobacteria为6.5%和5.5%。Flavobacterium和Pedobacter、Arthrobacter、Bacillus分别是CFB类、Actinobacteria、Firmicutes类中的优势属。分离到的天山1号冰川冰芯可培养细菌分属于4大类的14个属,Firmicutes类中属的种类最多,而Proteobacteria、Actinobacteria类和CFB类中,Frigoribacterium、Flavobacterium、Arthrobacter、Brevundimona、Pseudomonas和Pedobacter等属的细菌在天山冰芯的可培养菌株中为优势种类,在数量上占可培养细菌的90%以上。天山雪坑中的一些分离株在中性或碱性条件下生长,一些细菌能降解碳氢化合物、二苯并呋喃、有机氯化合物、苯酚等,这可能都与天山雪中的化学物质有关,可见,这种化学环境对天山细菌种类的分布有一定的选择作用。从1号冰川雪坑中分离出来的细菌与1号冰川植物中分离出的植物内生菌有一些相同属。植物中分离出来的细菌也有很多是天山雪坑样品中没有分离到的,应该是不同的生境有不同的选择作用的结果。天山雪坑细菌与Puruogangri、昆仑山和两极分离属有很多相同,说明这些种适应低温环境,能在不同的低温环境中保存下来,并且天山和Puruogangri、昆仑山有部分相同的沙尘爆来源;而与东绒布雪中的分离属比较,只有3个共有属,这种极大的差异性可能是它们主要的来源不同。雪坑中的细菌在数量和种类组成上的分布与季节性有很大相关性,而冰芯中微生物却没有呈现这种特征,主要是雪变冰的过程和淋溶作用等影响了微生物的分布,但在长时间尺度上冰芯中微生物信息也能反映气候信息。从雪坑和冰芯中分离出来的细菌多与从其他低温环境中分离出来的细菌有99%或98%的相似性,说明它们是适应低温的细菌,从天山雪坑和天山冰芯中分离的细菌只有4个属相同,而天山雪坑和天山冻土有11个共有属,天山冰芯和天山冻土有6个共有属,这三种不同的生境保存了不同的微生物类群,使微生物构成既有相似之处又有很大的区别,雪坑和冰芯样品中种类的巨大差别可能是不同时期微生物来源不同以及不同的生境进行选择的结果,源区微生物的种类构成、大气环流、沉降区的物理化学性质、沉积后作用以及微生物自身的种类构成等都是微生物种类和数量的重要影响因素,因此,研究保存在冰川中的微生物信息需要考虑更多这些因素的影响,这样才能更全面的反映过去的气候信息。更多还原

【Abstract】 Microorganisms in the glaciers which were atmospheric constituents originating from a variety of ecological sources at defined ages in history. The microbial community may occur transition after depositing by reproduction, decomposition, autolysis and meltwater washout and suffering the habitat changes of snow-ice. How these changes impact microbial distribution is vital important to unravel the relationship between microorganisms entrapped in deep ice core and climatic and environment. We study on microbial abundunce and structure of two snow pits and a shallow ice core intended to determine the mechanisms responsible for the process of microbial depositing on glacier .The major results were obtained as follows:The total cell number in different layers of snow pits ranged from 0.7×10³ to 2.16×10⁵ cells·mL^-1 and bacterial CFU varied from 0 to 550 cfu·mL^-1. It was 1.5:1 ratio of the average cell number in snow pit-2 samples to snow pit-1 samples, while the ratio of average CFU was 7.5:1. It might be because the conditions in May were much more favorable for bacterial recovery and growth. The vertical profiles of microbial distribution compared with Ca²⁺ concentrations at different depths appears cycles of peak value ranges and low value ranges, which might be related to the atmospheric circulation and ecological sources. The total cell number of the shallow ice core samples fluctuated from 1.4×10³ to 1.0×10⁵ cells·mL^-1 and bacterial CFU varied from 0 to 300 cfu·mL^-1. The cell counts and CFU within ice layers were higher than that within firn layers. This might be because of the percolation. The concentration of microorganisms in this shallow ice core decreased with increasing depth, which might be caused by changes of environment or by autolysis or being decomposited by other organisms. The amounts of total microorganisms and culturable bacteria have corresponding relationship but not instrictly. It indicated that the amount of culturable bacteria was also affected by the composition of bacteria other than ecologycal sources and bacteria generation.Isolates from two snow pits samples affiliated with 18 genera of 4 phylogenetic groups: Actinobacteria （Arthrobacter, Leifsonia, Microbacterium, Clavibacter, Rhodococcus, Nocardioides and one unclassified genus）, Firmicutes（Bacillus, Brevibacillus, Planococcus, Exiguobacterium and one unclassified genus）, Bacteroidetes （CFB group, Flavobacterium and Pedobacter） and Proteobacteria （Sphingomonas and Massilia and two unclassified genera）. CFB group, Actinobacteria, Firmicutes and Proteobacteria accounted for 53.5% and 54%, 26% and 28.5%, 14% and 12%, 6.5% and 5.5% of all bacterial isolates in snow pit-1 and snow pit-2 samples, respectively. The main genera of CFB、Actinobacteria、Firmicutes group were Flavobacterium, Pedobacter, Arthrobacter and Bacillus. Bacteria isolated from ice core samples belonged to 14 genera of 4 main phylogenetic groups. Actinobacteria contained 3 genera （Arthrobacter, Frigoribacterium and Kocuria） and the isolates were all from cold environments. Two genera （Flavobacterium and Pedobacter） affiliated with CFB group. Four genera （Brevundimonas, Janthinobacterium, Polaromonas and Pseudomonas） belong to the Proteobacteria. Firmicutes was consisted of 4 genera （Bacillus, Cohnella, Paenibacillus and Sporosarcina）. Firmicutes group contained the most genera. In Proteobacteria、Actinobacteria and CFB groups, Frigoribacterium、Flavobacterium、Arthrobacter、Brevundimona、Pseudomonas and Pedobacter were the dominant genera, which contained 90% of the total culturable bacteria.Some bacteria isolated from snow at No.1 Glacier can only survive when pH=7. Some can decomposite hydrocorbon compound, dibenzofuran, phenol and organochlorine compound, etc., which might be related with the chemical substances in snow. These implied that chemical condition was a selective factor for bacteria in glaciers. There were some common genera between snow isolates and plant isolates, but many isolates from plant cann’t isolated from snow, which might be the result of selection of different environments. At the same time, we found that there were some common genera between Tianshan snow isolates and Puruogangri, Kunlun Mountain and Polars isolates, which suggestted that these bacteria can fit to low temperature, and also, Tianshan Mountain and Puruogangri, Kunlun Mountain have some common dust sources regions. However, just three common genera existed between Tianshan snow and East Rongbuk glacier snow. It seems likely that variations in bacterial composition of diverse glacial snow could reflect changes in atmospheric circulation which affected different communities of bacteria and chemical environments for bacterial survival. The vertical distribution of microbial abundance and bacterial compositons was related with seasons. While microorganisms deposited in the ice haven’t showed this characteristic because of percolation but it also could reflect the atmospheric information on a long time scale.Isolates from snow and ice of Tianshan have 98% or 99% similarity with other cold environments’ isolates. In this study, just 4 common genera were found between snow pits and ice core samples, but members of 11 genera isolated from snow pits have been found in Tianshan permafrost, and 6 genera recovered from the ice core were found in Tianshan permafrost. This indicated three different environments deposited different microorganisms and made the different microbial community. The large difference between snow pits and ice core isolates might be caused by different sources and selective environments. Microbial abundunce and composition were affected by sources, atmoshperic circulation, physical and chemical characteristics of precipitation regions, post-depositional process and microbial community itself, etc. For reflecting atmoshperic information more accurately we should think about more factors affectting the process of microbial depositing on glacier.更多还原