内蒙古岗更诺尔湖泊退化情景下好氧甲烷氧化的微生物过程研究

Aerobic methane oxidation under distinct shrinkage scenario of Lake Ganggeng in Inner Mongolia Autonomous Region

摘要:

[目的]内蒙古岗更诺尔湖退化为碱地、草地情景下，研究好氧甲烷氧化过程及其微生物群落的变化规律。[方法]针对湖泊沉积物及其退化后形成的碱地、草地土壤，在不同初始甲烷浓度下培养，研究其甲烷氧化速率，通过实时荧光定量PCR、高通量测序技术分析甲烷氧化菌的群落构成及其变化规律。[结果]湖泊退化过程中，沉积物和碱地的土壤理化性质、甲烷氧化速率变化规律基本一致，但与草地土壤有显著差异。在微生物属水平，甲烷氧化菌Methylococcus的丰度显著增加，在沉积物、碱地和草地中的丰度分别为19.2%、48.8%和78.3%，而Crenothrix的丰度明显降低，依次为54.7%、32.1%、和13.9%。进一步室内模拟不同初始浓度下甲烷氧化过程，发现沉积物中Crenothrix和Methylocaldum的增幅最大；碱地土壤中Methylococcus和Methylomonas的增幅远高于其他甲烷氧化菌；而在草地土壤中，Crenothrix增加高达7.81%，增幅达196倍。这些显著增加的微生物可能在不同浓度甲烷氧化过程中发挥了重要作用。[结论]湖泊退化过程中，甲烷氧化潜力降低。沉积物中的甲烷氧化菌发生了显著分异，Methylococcus逐渐成为碱地和草地的优势微生物，而Crenothrix则逐渐成为弱势类群。然而，草地土壤氧化高浓度甲烷过程中，数量上占弱势的Crenothrix迅速变为优势类群，可能发挥了重要作用。

Abstract:

[Objective] To elucidate the variation patterns of aerobic methanotrophy under the shrinkage process from sediment to saline land and grassland. [Methods] Lake sediment, saline and grassland soils were collected from the shrinkage gradient of Lake Ganggeng in Inner Mongolia, and incubated under different initial CH₄ concentrations to determine their CH₄ oxidation potentials. We analyzed methanotrophic community composition and their abundance change by real-time quantitative PCR and high-throughput sequencing techniques. [Results] During lake shrinkage, soil properties of lake sediment and saline soil showed similar variation trends with methane oxidation rates, and were significantly different from that of grassland soil. In response to shrinkage, the relative abundance of Methylococcus increased significantly (with the relative abundance of 19.2%, 48.8% and 78.3% in lake sediment, saline and grassland soils, respectively), whereas Crenothrix decreased from 54.7% to 32.1% and 13.9%. Microcosm incubation of these samples under different initial CH₄ concentrations demonstrated the predominant increase of Crenothrix and Methylococcus in lake sediment; While Methylococcus and Methylomonas dominated the increase in saline soil; Crenothrix increased 7.81% in grassland soils (196 folds). [Conclusion] Lake shrinkage significantly decreased methane oxidation potential, and methanotrophic community also changed, with numerically dominant Methylococcus and Crenothrix in sediment and grassland respectively. However, it is noteworthy that under high CH₄ concentration, Crenothrix increased rapidly, most likely playing important roles during methane oxidation in all samples tested.