天山乌源1号冰川表面冰尘及底部沉积层真菌群落结构比较及其系统发育分析

Composition and phylogeny of fungal community in supraglacial cryoconite and subglacial sediments of the Glacier No.1 at headwaters of the rümqi River in Tianshan Mountains

对天山乌源1号冰川表面冰尘(Fz)及底部沉积层(Dz)的理化性质及真菌的多样性、群落结构、OTU的系统发育进行了比较分析。ITS克隆文库分析显示,依据99%相似性共得到26个真菌OTU,表面冰尘和底部沉积层分别为21和22个,其中17个为共有OTU。天山1号冰川中真菌以担子菌门(Basidiomycota)、子囊菌门(Ascomycota)占绝对优势,子囊菌门的真菌在Fz、Dz文库中的比例分别约为27%、57%。系统发育分析显示子囊菌门的真菌有14个OUT,8个属,其中Cladosporium仅分布在冰川表面(6.25%),而Aureobasidium仅出现冰川底部沉积层(8.93%)。另外6个属Tetracladium、Pseudeurotium、Fusarium、Penicillium、Simplicillium、Aspergillus在冰川底部和表面均有分布,但丰度明显不同,尤其是Aspergillus、Simplicillium在冰川底部沉积物中占优势(分别为17.86%、12.50%)。担子菌门的克隆主要来自Rhodotorula、Leucosporidium属,前者主要在分布冰川表面(12%),底部沉积层很少,后者在冰川表面及底部均有分布,分别占文库的比例为8.69%、12.50%。冰川表面和底部沉积层生态条件迥异,对其中的微生物系统发育类群具有明显的选择性。

The diversity, composition and phylogeny of fungal community in supraglacial cryoconites and subgla- cial sediments of the Glacier No. 1 in the headwaters of the Tianshan Mountains, China are assessed. Analysis of amplified rDNA ITS region sequences allows grouping of 203 clones into 26 operational taxonomic units （OTUs） using a cut-off of 99% identity. Twenty-two and twenty-one OTUs were found in the subglacial and supraglacial clone libraries, respectively. BLAST searches show that the subglacial community of the glacier was dominated by representatives of phylum Ascomycota （57% of clones）, followed by phylum Basidiomycota （18% of clones） and Chytridiomycota （7% of clones）, with the remainder of the library belonging to unclassified fungal OTUs （18% of clones）. The supraglacial cryoconite sample had 27% Ascomycota, 22% Basidiomycota and 2.2% Chytridiomycota, and 49% of remaining library clones could not classified. Of the total 26 OTUs, 14 are related to Ascomycota cluster of sequences, including the genera Cladosporium, Aureobasidium, Tetracladium, Pseudeurotium, Fusarium, Penicillium, Simplicillium, Aspergillus. Cladosporium, which were absent in the subglacial sediment, were only present in supraglacial cryoconite sample. No clones related to Aureobasidium, a dominant group in the subglacial sediment （ 8.93 % ）, were present in supraglacial cryoconite sample. The gene- ra Aspergillus （ 17.86% ） and Simplicillium （ 12.50% ）, which were rare in the supraglacial cryoconite library, were well represented in the subglacial sediment. In addition, Basidiomycota groups included relatives of Rhodotorula and Leucosporidium, of which the former well represented in the subglacial sediment （8.69%）, the latter being the dominant group in the subglacial and supraglacial clone libraries. As a result, different glacial environments would harbor unique assemblages of microbes because they arose from different sources and/or undergo specific selective pressures in situ.