Methane isotopologue fractionation during microbial methanogenesis and methonotrophy by pure and mixed laboratory cultures

纯和混合实验室培养物在微生物产甲烷和甲烷营养过程中的甲烷同位素分馏

• 批准号: 1852946
• 负责人: Shuhei Ono
• 金额: $ 27.45万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1852946&HistoricalAwards=false
• 关键词: Methane; isotopologue; fractionation; during; microbial

Methane is both an alternative energy source and a strong greenhouse gas. It is important to understand its sources and sinks for the future of our energy and environment. A group of microbes, called methanogens, is the major source of methane to the atmosphere as well as to methane hydrates in deep sediments. Methane is composed of one C and four H atoms. Each has two isotopes, 13C/12C and D/H, respectively. Microbial methane is often depleted in heavy isotopes of carbon and hydrogen as well as a doubly substituted isotopologue (13CH3D) because of the different reactivity of isotopologues (isotope substituted molecules). In this project, investigators will carry out a series of laboratory experiments, including bioelectrochemical systems and co-cultures, to examine the major control of methane isotopologue fractionations by methanogenic microbes. The goal is to construct a unified model that links isotopologue ratios of microbial methane to environmental and physiological parameters, in order to develop methane isotopologue ratios as a diagnostic tool for its source. The project will support a graduate student, and promotes partnership between the Massachusetts Institute of Technology and Aerodyne Research Inc. The laboratory of the investigator will participate in K-12 outreach programs to demonstrate microbial fuel cells and the use of isotopes in biogeochemistry. Carbon and hydrogen isotope ratios have been widely used to trace the origin of methane in the environment. In addition to bulk isotope ratios, the abundance of doubly substituted methane isotopologues (13CH3D) has been proposed as a gauge of methane formation temperature. While these proxies are used as a tool to fingerprint the source(s) of methane, they often yield data that are inconsistent with other geochemical parameters. This proposed research aims to identify the major control(s) of methane isotopologue fractionation during microbial methanogenesis and methanotrophy from a series of controlled laboratory culture experiments using 1) bioelectrochemical systems under well-defined redox potentials, 2) co-cultures of sulfate reducing bacteria and methanogens, and 3) cultures of aerobic and anaerobic methanotrophs. Four isotopologue compositions of methane (12CH4, 13CH4, 12CH3D, & 13CH3D) will be measured by a novel tunable infrared laser direct absorption spectroscopy (TILDAS) instrument. Investigators will test the hypotheses that the rate of methanogenesis or methanotrophy and the redox potential of the environment, rather than the pathway, impart the major control on isotopologue fractionation, and whether isotopologue equilibrium requires anaerobic oxidation of methane or other specific microbial community structures.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.

甲烷既是一种替代能源，也是一种强温室气体。了解碳源和碳汇对我们未来的能源和环境至关重要。一组被称为产甲烷菌的微生物是大气中甲烷以及深层沉积物中甲烷水合物的主要来源。甲烷由1个碳原子和4个氢原子组成。每个都有两个同位素，分别是13C/12C和D/H。微生物甲烷通常以重碳、重氢同位素以及双取代同位素（13CH3D）耗尽，因为同位素（同位素取代分子）的反应活性不同。在这个项目中，研究人员将进行一系列实验室实验，包括生物电化学系统和共同培养，以检查产甲烷微生物对甲烷同位素分馏的主要控制。目的是建立微生物甲烷同位素比率与环境和生理参数之间的统一模型，以发展甲烷同位素比率作为其来源的诊断工具。该项目将支持一名研究生，并促进麻省理工学院和Aerodyne研究公司之间的合作关系。研究人员的实验室将参与K-12外展项目，以展示微生物燃料电池和同位素在生物地球化学中的应用。碳和氢同位素比值已被广泛用于追踪环境中甲烷的来源。除了体积同位素比外，双取代甲烷同位素（13CH3D）丰度也被认为是甲烷地层温度的一个指标。虽然这些替代指标被用作识别甲烷来源的工具，但它们产生的数据往往与其他地球化学参数不一致。本研究旨在通过一系列受控的实验室培养实验，确定微生物产甲烷和产甲烷过程中甲烷同位素分馏的主要控制因素：1)氧化还原电位下的生物电化学系统；2)硫酸盐还原菌和产甲烷菌的共同培养；3)好氧和厌氧产甲烷菌的培养。利用一种新型可调谐红外激光直接吸收光谱仪（TILDAS）测量甲烷的四种同位素组成（12CH4、13CH4、12CH3D和13CH3D）。研究人员将测试以下假设：甲烷生成或甲烷化的速率和环境的氧化还原电位，而不是途径，对同位素分馏起主要控制作用，以及同位素平衡是否需要甲烷的厌氧氧化或其他特定的微生物群落结构。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。

项目成果

Rate limits and isotopologue fractionations for microbial methanogenesis examined with combined pathway protein cost and isotopologue flow network models

• DOI: 10.1016/j.gca.2022.03.017
• 发表时间: 2022-03
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: S. Ono;Jeemin H. Rhim;Eric C. Ryberg

Combined carbon, hydrogen, and clumped isotope fractionations reveal differential reversibility of hydrogenotrophic methanogenesis in laboratory cultures

• DOI: 10.1016/j.gca.2022.07.027
• 发表时间: 2022-08
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Jeemin H. Rhim;S. Ono