Biological Basis for Methane Synthesis in Oxic Lake Waters

湖泊和河流是陆地景观的一部分，但它们对陆地温室气体(GHG)平衡的贡献通常没有明确列入全球温室气体预算。二氧化碳是主要的温室气体，而甲烷是一种更强大、更持久的大气温室气体，被认为占全球变暖影响的20%-30%。在中断了几年后，大气中的甲烷水平再次上升，但到目前为止，将这种上升归因于源/汇的具体变化一直难以捉摸。准确预测淡水对全球CH4预算的贡献可能如何因环境条件的变化而改变，需要更好地从机械上理解形成CH4的所有生物过程。该项目的研究有可能有助于我们对生物甲烷生产的理解发生范式转变。到目前为止，这种微生物活动一直被认为是严格意义上的厌氧过程，然而最近的科学文献描述了在氧饱和的水环境中CH4的合成。在黄石湖也观察到了这种现象，这是一个在很大程度上受到保护的原始湖泊，不受人为输入的影响，因此代表了一个在组成和功能上都是自然的水生系统。该奖项的研究部分将侧重于确定在有氧环境中合成甲烷的生物学基础，并承诺为微生物生态学领域提供新的贡献，以及加强对生物圈中甲烷循环的理解。这个项目是合作的，两位首席研究人员将向博士后学者(人力资源开发)提供最先进的技术指导，后者将在实地和实验室活动中获得经验。这些学生将从蒙大拿州(美洲原住民)代表人数不足的群体中招募。调查人员将通过接触公共媒体和K-12学校的教师来继续他们更广泛的影响努力。CH4是一种生物气体，是全球碳循环的重要组成部分。虽然被认为是严格由产甲烷菌产生的，但在含氧海洋和淡水中发现了过饱和浓度的甲烷。被称为“甲烷悖论”的这一现象一直是旨在了解其生物学基础的重大努力的焦点。底栖环境中产甲烷菌的产生和甲基化化合物的有氧代谢可能在一定程度上起到了作用，但不能解释这种甲烷的大部分。相反，最近的报告指出了氧饱和环境中的产甲烷菌，甚至更矛盾的是，参与了产氧光养菌的参与。研究人员在黄石湖上的初步努力与这些新的观察结果一致，表明在氧气饱和的条件下会发生甲烷。这项拟议的研究旨在通过1)表征甲烷的分布和循环速率，并确定参与产甲烷的C底物，揭示黄石湖O2饱和水柱中上层甲烷富集区(PMEZ)矛盾形成的生物学基础；以及2)所涉及的生物的分离和表征。由该奖项资助的研究有望对潜在生物学、有趣的微生物协同关系的身份提供相当大的帮助，并有助于更全面地了解水环境中的碳循环。

Lakes and rivers are part of the terrestrial landscape, but their contributions to the terrestrial greenhouse gas (GHG) balance have typically not been explicitly included in global GHG budgets. CO2 is the dominant GHG, however CH4 is a more potent long-lived atmospheric GHG, and viewed to account for up to 20-30% of the global warming effect. Atmospheric CH4 levels are on the rise again after a hiatus of several years, yet attributing this rise to specific changes in sources/sinks has so far proved elusive. Accurately predicting how freshwater contributions to the global CH4 budget may be altered by changes to environmental conditions requires a better mechanistic understanding of all the biological processes that form CH4. Research in this project has the potential to contribute to a paradigm shift in our understanding of biological CH4 production. To date, this microbiological activity has been known to be a strictly anaerobic process, yet recent scientific literature has described CH4 synthesis in oxygen saturated aquatic environments. This phenomenon was also observed in Yellowstone Lake, a pristine lake that is largely protected from anthropogenic inputs and thus represents an aquatic system that is natural in composition and function. The research component of this award will focus on identifying the biological basis for CH4 synthesis in an oxic environment, and promises to provide novel contributions to the field of microbial ecology as well as an enhanced understanding of CH4 cycling in the biosphere. This project is collaborative, where both principal investigators will provide state-of-the-art technical guidance to a postdoctoral scholar (human resource development) who will gain experience in both field and lab activities. These students will be recruited from underrepresented groups from the state of Montana (Native Americans). The investigators will continue their broader impacts efforts by reaching out public media and K-12 school teachers.CH4 is a biogenic gas that is an important component of global carbon cycling. While viewed to be produced strictly by methanogens, it nevertheless is found at supersaturating concentrations in oxic marine and freshwaters. Known as the "methane paradox" this has been the focus of significant efforts aimed at understanding its biological basis. Generation by methanogens in benthic environments and aerobic metabolism of methylated compounds may contribute at some level, but cannot account for the bulk of this CH4. Rather, recent reports point to methanogens in oxygen saturated environments, and even more paradoxically, the involvement of oxygenic phototrophs. The preliminary efforts by the investigators on Yellowstone Lake are consistent with these novel observations and imply methanogenesis under oxygen saturating conditions. This proposed research aims to unveil the biology that underlies the paradoxical formation of the pelagic methane enriched zone (PMEZ) in O2 saturated water column of Yellowstone Lake by 1) characterization of methane distribution and cycling rates, and identification of the C substrate involved in methanogenesis; and 2) isolation and characterization of the organisms involved. Research funded by this award promises to shed considerable light on the identity of the underlying biology, interesting microbial synergistic relations and contribute to a more complete understanding of carbon cycling in aquatic environments.