天山乌鲁木齐河源1号冰川不同海拔可培养空气源酵母菌系统发育及多样性研究

为了了解天山乌鲁木齐河源1号冰川（简称乌源1号冰川）空气及气溶胶中可培养酵母菌的多样性、系统发育、空间分布及其与冰川生境酵母菌的关系，在乌源1号冰川西支3个海拔梯度位点收集空气气溶胶，采用4种培养基分离空气源酵母菌，根据菌落形态和显微镜镜检细胞形态初步分组，采用MSP-PCR指纹分型和rRNA基因间隔序列（ITS）确定酵母菌菌株的系统发育和分类地位，并分析了空气源酵母菌群落的多样性及空间分布特征。研究表明：从乌源1号冰川的表面空气共分离414株酵母菌，全部隶属于担子菌门（Basidiomycota），MSP-PCR指纹分型划分为53个基因型，代表菌株ITS基因测序结果显示隶属于9属28种，其中24种为伞菌亚门（Agariomycotina）成员，4种属于柄锈菌亚门（Pucciniomycotina），其中Holtermanniella、Vishniacozyma、Filobasidium、Dioszegia为优势酵母菌属。有6株酵母菌最适生长温度为16~18 ℃，为嗜冷菌，其余24株为耐冷菌，最适生长温度为22~25 ℃。Holtermanniella festucosa与Vishniacozyma victoriae为冰川空气广布的优势酵母菌种（22.22%、16.91%），其他大多为来自周边生境的耐冷酵母菌，在冰川生境均有分布。此外，在小幅度的海拔梯度上，3个海拔高度的空气酵母菌群落结构有所不同，但多样性指数没有显著差异。冰川生境酵母菌来源与其周边空气酵母菌密切相关，但以Holtermanniella属为代表的空气源优势酵母在冰川生境不能分离，说明冰川的严酷条件对外源微生物具有明显的选择作用。

Phylogeny and diversity of culturable airborne yeasts at different altitude on the Urumqi Glacier No. 1 in the Tianshan Mountains

Glaciers are known global reservoirs for cold-adapted microorganisms. Because of the special function of cryogenic microorganisms in glacial habitats， the cold-adapted yeast biodiversity is also of increasing interest to microbiologists. The aim of this investigation was to assess the occurrence and biodiversity of airborne yeast in the air and aerosol at different elevations on the surface of the Urumqi Glacier No.1 in the Tianshan Mountains， a well-known continental glacier （Northwest China）， and to test their temperature characteristic of growth. By using membrane filtration， air aerosol were collected at three sites on the surface of the west branch of the glacier （the altitude ranging from 3 950 to 4 090 m a.s.l.）. Isolation and purification of yeast were performed by four different agar media， and all yeast strains were preliminary grouped based on their colony and microscopic morphology. Taxonomic identity and genetic variability of strains isolated were determined by internal transcribed spacer （ITS） sequence and MSP–PCR fingerprinting. The results showed that all 401 isolates were identified as basidiomycetous yeasts （Agariomycotina and Pucciniomycotina）represented by 28 species of 9 genera （Holtermanniella， Vishniacozyma， Filobasidium， Dioszegia， Rhodotorula， Rhodosporidium， Cystofilobasidium， Naganishia and Papiliotrema）， with the first four being dominant genera. H. festucosa and V. victoriae was the dominant species （22.22% and 16.91%）. Among representative strains of the 28 yeast species， only six strains were psychrophilic （the optimum temperature for growth ranging from 16 to 18 ℃）， whereas the remaining 22 strains had the optimum temperature for growth ranging from 22 to 25 ℃， indicating that they belonged to psychrotolerant yeasts. Comparative analyses of Shannon， Simpson’s and Chao indices showed the community structures of culturable airborne yeasts at the three elevation ranges on the glacier surface were somewhat different， but differences between the diversity index were not significant. More remarkably， no strains of Holtermanniella， a dominant airborne yeast genus， ware not found in otherhabitatsof the glacier， such as cryoconite sediment and supra-glacial ice core， suggesting that the harsh conditions of glacier could exert a strong selective pressure on exogenous microorganisms.