祁连山冻土区土壤活动层与冻土层中甲烷代谢微生物群落结构特征

Methane metabolic microbial community structure in the active layer and the permafrost layer of the Qilian permafrost, China

冻土土壤中的甲烷代谢微生物可氧化或产生甲烷,影响着甲烷所参与的碳循环过程,对于全球温室气体的释放和调节具有重要的作用.对祁连山冻土区土壤活动层与冻土层中的甲烷代谢微生物产甲烷菌(Methanogens)和甲烷氧化菌(Methanotrophs)的群落结构组成进行研究.通过对产甲烷菌的mcrA基因和甲烷氧化菌的pmoA基因进行PCR扩增,分别构建其基因克隆文库,并通过序列同源比对进行系统发育分析和多样性分析.结果显示:冻土土壤活动层中的产甲烷菌包括Rice cluster Ⅰ、Methanosarcinaceae、Methanomicrobiales、Methanosaetaceae、Methanobacteriaceae五种类型,而在土壤冻土层则包括了Rice cluster Ⅰ、Methanosarcinaceae、Methanobacteriaceae三种类型.土壤活动层的甲烷氧化菌由隶属于α-Proteobacteria(Type Ⅱ)的Methylocystis和隶属于γ-Proteobacteria(Type Ⅰ)的Methylobacter两种类型群体组成,而土壤冻土层中则只包括了Methylocystis这一种类型.由此可见,冻土土壤活动层与冻土层中的甲烷代谢微生物群落结构存在一定的差异.

Methane metabolic microbial community in the permafrost soil can produce or oxidize methane, which affects processes of permafrost methane-cycling, therefore has an important role in the global greenhouse release and regulation. At present, research of methane metabolic microbial community structure in the soil of permafrost has received extensive attention. In order to understand the distribution and diversity of methane metabolic microbes in the permafrost, we studied the methanogen and methanotroph community compositions in the active layer and the permafrost layer of soils in Qilian Mountain, China. The molecular biology methods were used to amplify the methanogen mcrA genes and the methanotroph pmoA genes, then their gene clone libraries constructed. Phylogenetic analysis of the sequences based on sequence similarity was carried out and the community diversity was calculated. The retrieved methanogen mcrA genes sequences were classified into five lineages. The predominant groups of the active layer belonged to Rice cluster I, Methanosarcinaceae, Methanomicrobiales, Methanosaetaceae and Methanobacteriaceae, and those in the permafrost layer included Rice cluster I, Methanosarcinaceae and Methanobacteriaceae. All the methanotroph pmoA genes sequences were affiliated to the same phylum Proteobacteria. In the active layer, Proteobacteria was classified into two lineages including Methylocystis （a-Proteobacteria, type II） and Methylobacter （γ-Proteobacteria, type I）. In the permafrost layer, Methylocystis was the predominant lineage. The results indicated that there existed a certain difference in methane metabolic microbial composition between the active layer and the permafrost layer of soils in Qilian Mountain.