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氷河生態系は非常にシンプルな構造を持つため, 他の生態系では困難な, 総合的な生態系研究の理想的な対象となるばかりでなく, 雪氷微生物はアイスコア解析における古環境復元の新たな環境指標となることが報告されている. 氷河上には雪氷環境に適応したごく少数の種類のバクテリアが増殖し, それぞれ氷河上の異なる環境に適応している. また, 雪氷微生物は他の寒冷な環境からも検出されるが, 雪氷環境のみに特殊化した微生物ではなく, 土壌や淡水環境などにも多く生息していることが明らかになってきた. さらにここでは, 氷床アイスコア中の微生物解析についても議論する.Bacteria growing in the snow and ice of the glacier are important as decomposers of glacier ecosystems and bacteria in ice cores could be used as new environmental markers for past environmental studies. To clarify altitudinal changes in the bacterial community on the glacier, we analyzed bacterial 16S rRNA gene by PCR amplification. Analysis revealed the presence of 100 bacterial OTUs; however, 17 major OTUs accounted for 57-87% of the clone library at each site, suggesting that they formed the major part of the bacteria on the glacier. Based on the dominant phylotypes, the bacterial community on the glacier could be divided into three types, corresponding to the snow-covered, snow-and ice-covered, and bare-ice areas of the glacier. Our results suggest that a relatively limited number of bacteria predominate and that each phylotype is adapted to a distinct set of conditions on the glacier. Estimates by BLAST search of the source environments of relatives to the 16S rRNA gene sequences on the glacier suggest almost all were from soils and fresh waters,and very few from snow and ice environments. Based on geographical records in the database, all bacteria were matched to those recorded from the Polar Regions. The results suggest that the bacterial communities on the glacier are common in cold regions of the world and are likely to not be specialized members of the snow and ice biota but also inhabitants of soil and freshwater environments.
低温科学 70(-), 173-180, 2012
北海道大学低温科学研究所 = Institute of Low Temperature Science, Hokkaido University