EAGER: Chasing the elusive syntrophic partners in direct interspecies electron transfer

EAGER：在直接种间电子转移中追逐难以捉摸的互养伙伴

• 批准号: 2128365
• 负责人: Heyang Yuan
• 金额: $ 24.99万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128365&HistoricalAwards=false
• 关键词: EAGER; Chasing; elusive; syntrophic; partners

Anaerobic digestion is widely utilized worlwide to treat waste streams and convert them to biogas such as methane. Biogas fom anerobic digestion typically consists of 50-70% methane and thus needs to be treated to remove impurities including carbon dioxide and water vapor. To eliminate the need for addtional treatment and purification of biogas from existing anaerobic digesters, it is critical to understand and quantify the metabolic pathways of the microbial consortial involved in biogas production. The overarching goal of this high-risk and high-reward EAGER project is to characterize and quantify the metabolic pathways that drive methane production during anaerobic digestion. To advance this goal, the Principal Investigator (PI) of this project proposes to carry out an integrated experimental research program to test the hypothesis that interspecies hydrogen transfer (IHT) and direct interspecies electron transfer (DIET) play an equally important role during biogas production by methanogenesis in electrically conductive environments. The successful completion of this EAGER project could provide new fundamental knowledge that could be leveraged to develop and implement new engineering reactor design and operational strategies to increase the methane content of biogas produced by anaerobic digestors. Further benefits to society will be achieved through student education and training including the mentoring of a doctoral student. Interspecies hydrogen transfer (IHT) and direct interspecies electron transfer (DIET) have been shown to contribute to biogas production by methanogenesis in electrically conductive environments. However, a fundamental understanding and quantification of the relative contributions of IHT and DIET to methanogenesis have remained elusive due to the lack of experimental techniques to directly measure the associated microbial metabolisms and activities. The overarching goal of this project is to address this knowledge gap. To advance this goal, the Principal Investigator (PI) of this project hypothesizes that IHT and DIET play an equally important role during biogas production by methanogenesis in electrically conductive environments. This hypothesis is based on the results of preliminary studies by the PI that identified a novel Geobacter species (Candidatus Geobacter eutrophica) that was abundant in anerobic reactors supplied with conductive granular activated carbon. The PI also found that the Candidatus Geobacter eutrophica bacteria actively expressed genes encoding proteins for both extracellular electron transfer and hydrogen metabolism. To test this new hypothesis, the PI proposes to carry out an integrated experimental research program structured around two specific aims: 1) enrich DIET-capable Geobacter bacteria and elucidate their extracellular electron transfer mechanisms (Specific Aim 1) and 2) enrich DIET-capable methanogens and characterize their extracellular electron uptake mechanisms (Specific Aim 2). To enrich the DIET-capable Geobacter and methanogen bacteria, the PI proposes to use electrochemical stimulation in bioelectrochemical systems with specially designed electrodes. By combining cyclic voltammetry with measurements of biogas production, ion chromatography, resonance Raman microscopy and omics (metagenomics and metatranscriptomics), the PI hopes to unravel the metabolic pathways responsible for DIET in both electron-donating and electron-accepting microbial partners. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge to advance the development of new bioprocesses such as electro-methanogenesis that could convert waste streams to biogas with much higher methane yields than existing anerobic digestion reactors.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.

厌氧消化在世界范围内被广泛用于处理废物流并将其转化为甲烷等沼气。厌氧消化产生的沼气通常含有 50-70% 的甲烷，因此需要进行处理以去除包括二氧化碳和水蒸气在内的杂质。为了消除对现有厌氧消化池中沼气进行额外处理和纯化的需要，了解和量化参与沼气生产的微生物群落的代谢途径至关重要。这个高风险和高回报的 EAGER 项目的总体目标是表征和量化厌氧消化过程中驱动甲烷产生的代谢途径。为了推进这一目标，该项目的首席研究员（PI）建议开展一项综合实验研究计划，以检验种间氢转移（IHT）和直接种间电子转移（DIET）在沼气生产过程中发挥同等重要作用的假设通过导电环境中的产甲烷作用。该 EAGER 项目的成功完成可以提供新的基础知识，可用于开发和实施新的工程反应器设计和操作策略，以增加厌氧消化器产生的沼气的甲烷含量。通过学生教育和培训，包括博士生的指导，将进一步造福社会。种间氢转移（IHT）和直接种间电子转移（DIET）已被证明有助于在导电环境中通过产甲烷产生沼气。然而，由于缺乏直接测量相关微生物代谢和活动的实验技术，对 IHT 和 DIET 对产甲烷作用的相对贡献的基本理解和量化仍然难以捉摸。该项目的总体目标是解决这一知识差距。为了推进这一目标，该项目的首席研究员 (PI) 假设 IHT 和 DIET 在导电环境中通过产甲烷作用生产沼气过程中发挥着同样重要的作用。这一假设基于 PI 的初步研究结果，该研究确定了一种新的地杆菌属（Candidatus Geobacter eutropica），该物种在配有导电颗粒活性炭的厌氧反应器中含量丰富。 PI 还发现，Candidatus Geobacter eutropica 细菌积极表达编码细胞外电子转移和氢代谢蛋白质的基因。为了检验这一新假设，PI 建议围绕两个具体目标开展一项综合实验研究计划：1）丰富具有 DIET 能力的地杆菌并阐明其细胞外电子转移机制（具体目标 1）和 2）丰富具有 DIET 能力的地杆菌属细菌。产甲烷菌并表征其细胞外电子摄取机制（具体目标 2）。为了丰富具有 DIET 能力的地杆菌和产甲烷菌，PI 建议在具有特殊设计电极的生物电化学系统中使用电化学刺激。通过将循环伏安法与沼气产量、离子色谱、共振拉曼显微镜和组学（宏基因组学和宏转录组学）的测量相结合，PI 希望揭示电子供给和电子接受微生物伙伴中负责 DIET 的代谢途径。该项目的成功完成有可能产生变革性影响，通过产生新的基础知识来推动新生物工艺的发展，例如电产甲烷，可以将废物流转化为沼气，其甲烷产量比现有的厌氧消化反应器高得多。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。