RUI: Methanogenesis from quaternary amines

该项目将研究产生甲烷的微生物利用一类重要的、尚未得到充分研究的化合物产生甲烷的机制。甲烷是天然气的重要组成部分，在全球碳循环和大气过程中起着重要作用。一些产甲烷微生物（产甲烷菌）最近被证明可以将一组称为季胺（QAs）的化合物转化为甲烷。QAs在许多不同的环境中都是丰富的化合物，人类肠道中的甲烷生成与心脏病的发展有关。目前关于产甲烷菌如何将QAs转化为甲烷以及这一过程在环境中有多普遍的知识明显缺乏。这种知识上的差距导致计算机生成的模型预测地球大气中甲烷生成作用的潜在不准确性。本研究项目将通过1)通过QAs研究甲烷生成的生理机制和2)在不同环境中鉴定和量化负责这一过程的微生物来解决这一知识空白。这项研究也将使迈阿密大学汉密尔顿分校的学生受益，汉密尔顿分校是迈阿密大学社区部门的一部分，为第一代、社会经济地位较低和代表性不足的少数群体的学生提供服务。这些学生将通过课堂活动和本科研究为研究项目做出贡献。季胺（QAs）是一种丰富的天然化合物，近年来作为微生物在缺氧环境中的重要底物出现，包括产甲烷菌。QAs的分解对从全球生物地球化学循环到人类动脉粥样硬化的多种过程具有直接影响。对产甲烷古菌对QAs的厌氧分解代谢机制（即QA去甲基化）的了解尚缺乏。早期的数据表明，来自COG5598蛋白家族的缺乏pyrlysine（非pyl）甲基转移酶与同源的corcoroid结合蛋白一起参与了qa依赖的甲烷生成，但这些途径尚未被阐明。确定该家族多个酶的功能将有助于更好地确定COG5598成员在甲烷生产中的作用。该提案的核心假设是，非pyl COG5598酶负责QA去甲基化和QA依赖甲烷生成的启动，作为三组分corcorid依赖甲基转移途径的一部分，并且编码这些途径的生物体可以在环境中被识别出来。在这项工作中，研究人员将：1)利用比较蛋白质组学和生物化学技术确定甘氨酸甜菜碱和四甲基铵依赖的甲烷生成途径；2)确定在不同环境中预测的利用甲烷生成菌的身份和相对丰度。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will investigate mechanisms by which methane-producing microorganisms can utilize an important and understudied class of compounds to produce methane. Methane, the key component of natural gas, plays an important role in global carbon cycling and atmospheric processes. Some methane-producing microbes (methanogens) have recently been shown to convert a group of compounds called quaternary amines (QAs) to methane. QAs are abundant compounds in many different environments, and methanogenesis in the human gut has been linked to the development of heart disease. Current knowledge of how methanogens can convert QAs to methane and how prevalent this process is in the environment is distinctly lacking. This gap in knowledge leads to potential inaccuracies in computer-generated models predicting the role of methanogenesis on Earth's atmosphere. This research project will address this gap in knowledge by 1) investigating the physiological mechanisms of methanogenesis via QAs and 2) identifying and quantifying the microorganisms responsible for this process in different environments. This research will also benefit students at the Miami University Hamilton, part of a community-based division of Miami University that serves students from first-generation, lower socioeconomic status, and under-represented minority groups. These students will contribute to the research project through classroom activities and undergraduate research.Quaternary amines (QAs) are abundant natural compounds that have recently emerged as important substrates for microbes in anoxic environments, including methanogens. The breakdown of QAs has direct implications for diverse processes from global biogeochemical cycling to atherosclerosis in humans. Understanding of the mechanisms of anaerobic catabolism of QAs by methanogenic archaea, namely QA demethylation, is lacking. Early data suggest that pyrrolysine-lacking (non-pyl) methyltransferases from the COG5598 protein family are involved in QA-dependent methanogenesis along with cognate corrinoid binding proteins, but these pathways have not been elucidated. Determining the function of multiple enzymes from this family will facilitate better identification of the role of members of COG5598 in methane production. The central hypothesis of this proposal is that non-pyl COG5598 enzymes are responsible for QA demethylation and initiation of QA-dependent methanogenesis as part of a three-component corrinoid-dependent methyl transfer pathway, and that organisms encoding these pathways can be identified within the environment. In this work the investigators will: 1) identify pathways for QA-dependent methanogenesis from glycine betaine and tetramethylammonium using comparative proteomics and biochemistry techniques, and 2) determine the identities and relative abundance of predicted QA-utilizing methanogens in different environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.