祁连山冻土区水合物DK3和DK6钻孔中微生物脂肪酸特征及意义

利用脂肪酸法分析祁连山冻土带水合物区DK3(含水合物)与DK6(不含水合物)钻孔岩心中微生物多样性。本研究获得C12到C24二十六种脂肪酸(FA),可以分成直链饱和脂肪酸(SSFA),支链饱和脂肪酸(BSFA),单键不饱和脂肪酸(MUFA),环丙烷脂肪酸(CFA)和多键不饱和脂肪酸(PUFA)五大类型,其中SSFA相对含量最高。由于特异性的脂肪酸指示特异性的微生物类群,得出两根岩心中微生物类群主要由革兰氏阳性菌、革兰氏阴性菌和真菌组成。运用PAST(Palaeontological statistics,version 1.21)软件对已获得的脂肪酸进行主成分分析和聚类分析,得出DK3与DK6岩心的微生物组成并无显著性差异,但是DK3岩心中含水合物层位与不含水合物层位微生物组成有差异,DK6岩心中有水合物异常的层位与无异常的层位有差异。发现C16:1和C18:1这两类脂肪酸与甲烷异常有很好的对应关系,从另一方面证明了水合物异常影响微生物组成分布。本次研究首次获得冻土沉积物中FA组成特征,丰富了FA的分布范围,研究结果扩大了真菌的分布深度,具体机理有待更多的实验证明。

Discrimination of Microbial Diversity by Fatty Acid in Drill Hole DK3 and DK6 in a Gas Hydrate Area, Qilian Mountain Permafrost

The fatty acid (FA) method was used to evaluate microbial community diversity in (gas hydrate-bearing) Drill Hole DK3 and (hydrate-absent) Drill Hole DK6 in Qilian Mountain permafrost. 26 kinds of FA obtained in this study were divided into five types: BSFA, MUFA, CFA, PUFA and SSFA, with SFA being the dominant component. Microbial community of the cores from the two drill holes contain gram positive bacteria, gram negative bacteria and fungi classified from specificity FA. Principal component analysis and cluster analyses of FA from the two cores were performed using the PAST (palaeontological statistics, version 1.21) program. No significant difference of microbial components was observed between DK3 and DK6, but there did exist obvious difference of microbial components between gas hydrate-bearing (or methane anomaly) layer and hydrate-absent (or methane anomaly-absent) layer. The authors found that C16:1, C18:1 and methane anomaly have very good corresponding relationship. These phenomena prove from another side that methane concentration and gas hydrate may affect microbial habitats in Drill Hole DK3 and DK6. This is the first study of FA composition characteristics in permafrost sediments, and the results enrich the distribution range of FA and also expand the distribution depth of fungi; nevertheless, more experiments are needed to prove the specific mechanism.