Collaborative: Microbial chain elongation-mediated dehalogenation and carbon transformation

氯化溶剂由一大类氯化碳氢化合物组成，在世界范围内已大量使用，以支持各种工业应用。氯化溶剂，如全氯乙烯（PCE）和三氯乙烯（TCE）是美国和全世界最普遍的地下水污染物之一。麦卡蒂藻（dehalococoides mccartyi）生物修复技术是一种很有前途的处理地下水PCE和TCE污染的技术。麦卡蒂脱盐coccoides mccartyi是一种厌氧微生物，可将PCE和TCE还原并转化为乙烯，乙烯随后可被地下水中存在的其他厌氧和/或好氧微生物矿化为二氧化碳。然而，Dehalococcoides mccartyi需要使用氢（H2）作为唯一的电子供体将PCE和TCE转化为乙烯。该项目的总体目标是研究微生物链延伸介导的脱卤化作为一种新型地下水生物修复工艺的使用，该工艺利用厌氧微生物组合的能力，产生所需的氢气，以使用乳酸、糖蜜和植物油等有机底物将PCE/TCE还原并转化为乙烯。该项目的成功完成将通过产生新的基础知识来促进开发和实施更有效和更具成本效益的生物修复技术来处理受氯化溶剂污染的地下水，从而造福社会。通过教育和拓展活动，包括指导亚利桑那州立大学和佛蒙特大学的两名研究生和两名本科生，将为社会带来额外的好处。麦卡蒂脱卤coccoides mccartyi是一种有机卤素呼吸细菌，在厌氧呼吸过程中利用卤化化合物作为终端电子受体，利用氢（H2）等电子供体产生生长所需的能量。在过去的二十年中，麦卡蒂脱盐球菌（Dehalococcoides mccartyi）已成为最有前途的微生物，具有对污染地下水中的氯化碳氢化合物（如过氯乙烯（PCE）和三氯乙烯（TCE））进行还原脱卤的能力。然而，地下水中利用H2作为电子供体的竞争微生物（如铁或硫酸盐还原菌）会对麦卡蒂脱卤菌对PCE/TCE脱卤和转化为乙烯的速度和程度产生不利影响。这种竞争一直与PCE/TCE脱卤速度缓慢和/或氯乙烯等有毒中间体的积累有关。基于有希望的初步研究结果，该项目的主要研究者（pi）提议探索微生物链伸长与还原性脱卤的耦合，目的是确定一个厌氧微生物联盟，该联盟可以减少PCE/TCE并将其转化为乙烯，同时使用链伸长产生进行这种转化所需的H2。为了实现这一目标，pi建议开展综合实验和建模研究计划，以1)揭示控制微生物链延伸介导的脱卤的关键代谢途径和生态相互作用，以及2)开发和验证微生物链延伸耦合脱卤的计算代谢模型。本研究的具体目标是：1)表征有机卤化物呼吸和链延长细菌联盟的生长和抑制动力学和代谢网络，这些细菌已显示出将PCE/TEC转化为乙烯的潜力；2)揭示微生物链延长与有机卤化物呼吸微生物群落中甲烷生成和同质丙酮生成的竞争代谢途径的相互作用。通过产生新的基础知识和计算代谢模型，本研究的成功完成有可能产生变革性影响，以推进微生物链延伸介导的地下水生物修复的开发和部署。为了实现该项目的教育和培训目标，pi建议利用各自机构的现有项目，将研究结果整合到亚利桑那州立大学的RET（教师研究经验）项目和佛蒙特大学（UVM）的扩展项目（4-H）中，以教授和激励高中教师和学生探索微生物在环境修复中的应用。此外，pi计划利用亚利桑那州立大学和弗吉尼亚大学现有的REU（本科生研究经验）项目，从代表性不足的群体中招募本科生参与该项目。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。

Chlorinated solvents consist of a large family of chlorinated hydrocarbons that have been used worldwide in large quantities to support various industrial applications. Chlorinated solvents such as perchloroethylene (PCE) and trichloroethylene (TCE) are among the most ubiquitous groundwater contaminants in the United States and worldwide. Bioremediation using Dehalococcoides mccartyi has emerged as a promising technology to treat groundwater contaminated by PCE and TCE. Dehalococcoides mccartyi are anaerobic microorganisms that can reduce and convert PCE and TCE to ethene which can subsequently be mineralized to carbon dioxide by other anerobic and/or aerobic microorganisms present in groundwater. However, Dehalococcoides mccartyi require the use of hydrogen (H2) as a sole electron donor to convert PCE and TCE to ethene. The overarching goal of this project is to investigate the use of microbial chain elongation-mediated dehalogenation as a novel groundwater bioremediation process that leverages the ability of a consortium of anaerobic microorganisms to produce the amount of H2 required to carry out the reduction and conversion of PCE/TCE to ethene using organic substrates such as lactic acids, molasses, and vegetable oil. The successful completion of this project will benefit society through the generation of new fundamental knowledge to advance the development and implementation of more efficient and cost-effective bioremediation technologies for the treatment of groundwater contaminated by chlorinated solvents. Additional benefits to society will be achieved through education and outreach activities including the mentoring of two graduate students and two undergraduate students at Arizona State University and the University of Vermont.Dehalococcoides mccartyi are organohalide-respiring bacteria that utilize halogenated compounds as terminal electron acceptors in an anaerobic respiration process to generate the energy required for their growth using electron donors such as hydrogen (H2). During the last two decades, Dehalococcoides mccartyi have emerged as the most promising microorganisms with capability to carry out the reductive dehalogenation of chlorinated hydrocarbons such as perchloroethylene (PCE) and trichloroethylene (TCE) in contaminated groundwater. However, competing microorganisms (e.g., iron or sulfate reducing bacteria) in groundwater that utilize H2 as electron donor can adversely impact the rate and extent of PCE/TCE dehalogenation and conversion to ethene by Dehalococcoides mccartyi. This competition has been consistently linked to slow rates of PCE/TCE dehalogenation and/or the accumulation of toxic intermediates such as vinyl chloride. Building upon the results of promising preliminary studies, the Principal Investigators (PIs) of this project propose to explore the coupling of microbial chain elongation with reductive dehalogenation with the goal of identifying a consortium of anaerobic microorganisms that can reduce and convert PCE/TCE to ethene while using chain elongation to generate the amount of H2 required to carry out this conversion. To advance this goal, the PIs propose to carry out an integrated experimental and modeling research program to 1) uncover critical metabolic pathways and ecological interactions that govern microbial chain elongation-mediated dehalogenation, and 2) develop and validate computational metabolic models of microbial chain elongation coupled with dehalogenation. The specific objectives of the research are to: 1) Characterize the growth and inhibition kinetics and metabolic networks of a consortium of organo-halide respiring and chain-elongating bacteria that has shown promising potential to convert PCE/TEC to ethene and 2) Unravel the interactions of microbial chain elongation with the competing metabolic pathways of methanogenesis and homoacetogenesis in organo-halide respiring microbial communities. The successful completion of this research has the potential for transformative impact through the generation of new fundamental knowledge and computational metabolic models to advance the development and deployment of groundwater bioremediation by microbial chain elongation-mediated dehalogenation. To implement the educational and training goals of this project, the PIs propose to leverage existing programs at their respective institutions to integrate the findings from this research into an RET (Research Experience for Teachers) program at Arizona State University and an extension program (4-H) at the University of Vermont (UVM) to teach and inspire high school teachers and students to explore the use of microorganisms in environmental remediation. In addition, the PIs plan to leverage existing REU (Research Experiences for Undergraduates) programs at ASU and UVM to recruit undergraduate students from underrepresented groups to work on the project.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.