青藏高原湿地低温甲烷代谢途径及其功能产甲烷菌的温度适应机制

Natural wetlands contribute approximate 20% atmosphere methane. Permafrost presently covers approximately 25% of the earth’s land area and contains vast amounts of biogenic methane (over 5000 Tg in the ice portion alone) and organic carbon attributed to the lower microbial degradation at cold. Global warming caused permafrost melting and temperature increasing could lead to a sudden release of methane into the atmosphere. Therefore, it is essential to understand the methane metabolic pathways and the performers, methanogenic Archaea, and the mechanisms of them in adaptation of temperature changing. Tibetan Plateau is widely distributed of cold wetlands. Our previously molecular ecological survey on Zoige wetland indicates that methylotrophic and aceticlastic methanogenic Archaea are prevalent in the wetland. Investigation of the methane production pathways in Zoige wetland soil microcosme predicted that methylotrophic methanogenic pathway contributed proximate 20% methane emission in Zoige wetland. Therefore, the goals of this project, by selecting three cold lakes and the lakeside wetlands at Tibetan Plateau as subjects, are to disclose low temperature methane production pathways prevalent in the cold lake sediments and wetlands. By using the cold adaptive methanogen strains we have obtained from Zoige wetland and other cold Tibetan wetlands as models, we want to study the cold adaptive mechanisms of methanogenic Archaea by particular focusing on posttranscriptional level. According to that a previously isolated psychrophilic methanogen R15 becomes “mesophilic” after 10-year laboratory culturing, we will study the evolution mechanism of Archaea in adaptation of elevated temperature by focusing on the cell surface protein glycosylation. In addition, we will probe whether anaerobic methane oxidation occurs in the cold wetland, in particularly that coupled to nitrite reduction according to high nitrite present in Zoige wetland. The study would disclose cold active methane production pathway and maybe anaerobic methane oxidation process in Tibetan wetlands.

湿地贡献了20%的大气甲烷。低温湿地储存了大量有机碳，全球变暖导致微生物代谢产甲烷活力的提高可能使低温湿地由碳汇变为碳源。因此，认识低温湿地甲烷代谢途径及功能微生物及其温度响应机制，将对全球变暖趋势下低温湿地释放更多温室气体提供预警指导。我国青藏高原遍布低温湖泊和湿地，我们前期对若尔盖湿地的分子生态学调查发现湿地中含有多样性丰富的甲烷古菌, 并发现甲基产甲烷途径在该湿地的甲烷排放中重要。本项目选择青藏高原代表性低温湖泊沉积物及湖滨湿地为对象, 拟揭示其中低温活跃的甲烷代谢途径,研究优势的嗜/耐冷甲烷古菌的低温适应机制，尤其转录后调控在冷适应中的作用，以及适应温度升高的进化机制; 探讨低温湿地的甲烷厌氧氧化过程,特别是偶联于亚硝酸盐还原的甲烷氧化。预期该研究将揭示青藏高原低温湿地中的优势甲烷代谢和厌氧降解途径及其环境影响因子，并可能发现新的低温甲烷代谢途径及低温甲烷古菌的升温进化机制。

湿地贡献了大气20%的甲烷，而甲烷古菌是唯一大量产生甲烷的生物。低温湿地因微生物活力低储存了大量有机碳，全球变暖导致微生物代谢产甲烷活力的提高可能使低温湿地由“碳汇”变为“碳源”。我国青藏高原遍布低温湖泊和湿地，前期对若尔盖湿地的分子生态学调查发现多样性丰富的甲烷古菌, 并发现甲基产甲烷途径在该湿地的甲烷排放中重要。本项目以青藏高原代表性低温湖泊沉积物及湖滨湿地为对象, 研究低温活跃的甲烷代谢途径和关键的嗜/耐冷甲烷古菌的低温适应机制，及其它们适应温度升高的进化机制; 探讨低温湿地的甲烷厌氧氧化过程。项目实施4年取得了如下成果：1）从若尔盖湿地获得偶联Fe3+的低温厌氧甲烷氧化菌新种Ca. Methanoperedens psychrophilus的富集物及其基于宏基因组组装的基因组，并分析了其可能的嗜冷机制；2）证明mRNA加工是低温活跃的甲基产甲烷途径的转录后调控机制；3）揭示了mRNA加工酶的工作机制及其古菌 rRNA加工成熟途径；4）发现玉米黄质与冰川细菌在低温及寡营养时的光能利用相关； 5）发现嗜冷甲烷古菌的小热休克蛋白具有保护蛋白的抗氧化活力；6）证明S-layer 蛋白N-糖基化是嗜冷甲烷古菌“进化”为中温菌的基础；7）报道了首个古菌全局转录终止因子- aCPSF1及其介导的古菌转录终止机制是真核的简化模式；8）报道首个古菌冷休克蛋白TRAM及其发挥的组学水平转录后调控功能。 共发表文章14篇，其中SCI文章13篇，授权专利1项。圆满完成了项目的目标。这些阐明了青藏高原低温湿地中的低温活跃的甲烷代谢途径、及其功能低温甲烷古菌的温度响应机制，可对全球变暖趋势下微生物降解有机质释放更多温室气体提供预警性指导。