不同水分条件下格陵兰岛冻土活性甲烷氧化菌群落分异规律

揭全球气候变化导致丹麦格陵兰岛形成了旱地和间歇淹水的土壤景观,采用稳定性同位素核酸探针技术和高通量测序16S r RNA及pmoA基因的分析方法,开展了格陵兰岛旱地和间歇淹水土壤微宇宙培养试验,探究不同水分条件下冻土的甲烷氧化潜力及活性好氧甲烷氧化菌群落演替规律。结果表明:与旱地土壤相比,淹水土壤氧化高浓度甲烷的速率呈现降低趋势,分别为12.38和12.17μg/(g·d),但后者对甲烷碳同化利用效率显著高于前者,土壤~(13)C-有机碳原子百分比从自然丰度1.08%,分别增加至1.64%和1.99%。超高速密度梯度离心分析~(13)C-DNA发现甲烷氧化菌群落发生演替,旱地土壤中Crenothrix甲烷氧化菌16S rRNA基因丰度仅为0.04%,而在间歇淹水土壤中为23.78%,增幅高达557倍;类型Ⅱ甲烷氧化菌Methylosinus则从33.76%增至44.38%。然而,类型Ⅰ甲烷氧化菌Methylocaldum的丰度明显降低,从旱地土壤10.15%显著降低为间歇淹水0.14%;进一步通过pmo A基因高通量测序分析,也得到了类似的结果,特别是类型Ⅰ甲烷氧化菌RPCs从旱地土壤15.61%显著降低至间歇淹水土壤的0.13%。这些结果表明:尽管格陵兰冻土中经典的类型Ⅱ甲烷氧化菌主导了旱地土壤和间歇性淹水土壤好氧甲烷氧化过程,但水分可能是甲烷氧化菌群落演替的重要环境驱动力,水分增加导致活性的类型Ⅰ种群丰度降低,同时显著刺激了新型甲烷氧化菌Crenothrix的大量生长并可能在间歇淹水土壤中发挥了重要作用。

The Emergence of Novel Methane Oxidizers in Greenland Permafrost Soil Under Periodically Water Saturated Conditions

This study investigated the impact of soil moisture on methane oxidation potential and the species of active methanotrophs in upland and periodic drowned grassland. Two contrasting soil types: permanent aerobic upland and periodic drowned grassland, were collected from Zackenberg, Greenland. Each soil samples were incubated in the 120ml bottles with 5% ₁₃C-methane in the experimental group or with air in the control treatments. The stable isotope probing technology was used to labeling the active methanotrophs, while high throughput sequencing of the 16S rRNA and pmoA gene were performed to analyze how the active methanotrophs changes in abundance and composition in response to the different soil moisture. Both soil samples showed high activity of aerobic methane oxidation, while the periodic drowned grassland developed the superior ability of carbon assimilation. The difference between those species with subprime status in two types of soil samples may explained the variance of soil methane oxidation and carbon assimilation. The results indicated that the periodically draining actually strengthen the methane oxidation by altering the composition of subordinate active methanotrophs(Methylocaldum and Crenothrix)rather than the dominant ones (Methylocystis/Methylosinus) in permafrost soil.