Uncovering novel microbial ecological relationships that foster enhanced pollutant biodegradation rates in contaminated groundwater systems

氯乙烯（VC）是一种已知的致癌物质和常见的地下水污染物，可能会对饮用水供应产生负面影响。虽然已知一些细菌可以从地下水中去除VC，但对这些生物的生态学知之甚少，特别是在地下水中经常出现的低氧条件下。对这些生物之间的相互作用以及与生态系统中其他细菌的相互作用的基本理解的提高可能会导致新的补救策略的发展。拟议的工作将通过开发基于微生物生态学的更精确和可持续的修复策略来造福社会。其他更广泛的影响包括培训本科生和研究生将微生物生态学工具应用于环境问题，增加工程中代表性不足的群体的参与，与环境专业人员和监管机构分享研究成果，并为有兴趣追求科学，技术，工程和数学（STEM）主题的高中生提供研究机会。如果成功，这项研究将提供有价值的工具，以帮助确保国家的水安全。VC通常是由广泛使用的氯化溶剂四氯乙烯和三氯乙烯的不完全厌氧生物降解产生的。由于厌氧VC脱氯细菌，和产氧氮循环细菌产生的产品，可以是有用的初级和共代谢底物和电子受体的VC氧化剂，据推测，这些微生物群之间有新的生态关系在好氧/缺氧界面或在VC污染的网站在低水平的氧通量的区域。本研究将探讨好氧VC氧化细菌和厌氧VC脱氯细菌之间的相互作用，在低氧通量污染的地下水环境中，以确定潜在的显着积极影响，这些相互作用对VC的生物降解速率。调查将包括三项具体任务：1）在实验室微观世界中演示VC的同时氧化和还原; 2）调查VC氧化剂、厌氧VC脱氯剂和VC污染场地沉积物样本中潜在产氧细菌之间的空间关系; 3）调查低溶解氧（DO）实验室微观世界中潜在的种间氧转移关系。现场样品将通过定量PCR和荧光原位杂交共聚焦扫描激光显微镜进行分析，以研究沉积物样品中VC氧化剂，厌氧VC脱氯剂和潜在产氧细菌之间的空间关系。微观研究，包括使用氧渗透管，以创建低DO通量条件，将用于模拟这些生物体之间的相互作用。最后，氧稳定同位素将被用来研究微观世界中潜在的物种间氧转移关系。该项目将揭示需氧和含氧氮循环微生物在介导地下生物降解反应中的重要作用。进一步了解好氧过程对VC生物降解速率的贡献，将促进不同微生物群落和VC衰减之间的预测定量关系的变革性发展。通过开发更可持续和精确的补救方法，包括更有针对性的电子供体/受体注射或开发能够增强VC生物降解的生物强化培养物，可以实现对受氯化溶剂污染的地下水的管理的改善。这种对地下系统中有氧生物降解过程的更好理解也可以扩展到氯化乙烯以外的化合物，因为含氧和低氧通量情景与各种地下生物降解过程有关。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Vinyl chloride (VC) is a known carcinogen and common groundwater pollutant that may negatively impact drinking water supplies. Although some bacteria are known to remove VC from groundwater, little is known about the ecology of these organisms, especially under the low oxygen conditions that often occur in groundwater. An improved fundamental understanding of the interactions between these organisms, as well as interactions with other bacteria in the ecosystem may lead to the development of novel remediation strategies. The proposed work will benefit society by developing more precise and sustainable remediation strategies based on microbial ecology. Additional broader impacts include the training of undergraduate and graduate students to apply microbial ecology tools to environmental problems, increasing the participation of underrepresented groups in engineering, sharing research findings with environmental professionals and regulators, and providing research opportunities to high school students interested in pursuing Science, Technology, Engineering, and Math (STEM) topics. If successful, this research will provide valuable tools to help ensure the Nation's water security.VC is typically generated by incomplete anaerobic biodegradation of the widely used chlorinated solvents tetrachloroethene and trichloroethene. Because anaerobic VC dechlorinating bacteria, and oxygenic nitrogen-cycling bacteria generate products that can be useful as primary and cometabolic substrates and electron acceptors for VC-oxidizers, it is hypothesized that there are novel ecological relationships between these microbial groups at oxic/anoxic interfaces or in regions of low-level oxygen flux at VC contaminated sites. This research will probe the interactions between aerobic VC-oxidizing bacteria and anaerobic VC-dechlorinating bacteria at low oxygen fluxes in contaminated groundwater environments to identify potential significant positive impacts of these interactions on VC biodegradation rates. The investigations will include three specific tasks: 1) Demonstrate simultaneous oxidation and reduction of VC in laboratory microcosms; 2) Investigate spatial relationships between VC-oxidizers, anaerobic VC-dechlorinators, and potential oxygen-producing bacteria in sediment samples from a VC-contaminated site; and 3) Investigate potential interspecies oxygen transfer relationships in low dissolved oxygen (DO) laboratory microcosms. Field samples will be analyzed by quantitative PCR and fluorescence in situ hybridization-confocal scanning laser microscopy to study spatial relationships between VC-oxidizers, anaerobic VC-dechlorinators, and potential oxygen-producing bacteria in sediment samples. Microcosm studies, including the use of oxygen permeation tubes to create low-DO flux conditions, will be used for modeling the interactions between these organisms. Finally, oxygen stable isotopes will be employed to investigate potential interspecies oxygen transfer relationships in microcosms. This project should reveal the important roles that aerobic and oxygenic nitrogen-cycling microorganisms play in mediating subsurface biodegradation reactions. An improved understanding of the contribution of aerobic processes to VC biodegradation rates will spur the transformative development of predictive quantitative relationships between the diverse microbial communities and VC attenuation. Improvements in management of groundwater contaminated with chlorinated solvents could be realized by developing more sustainable and precise approaches to remediation that involve more targeted electron donor/acceptor injections or developing bioaugmentation cultures capable of enhanced VC biodegradation. This improved understanding of aerobic biodegradation processes in subsurface systems could also extend to compounds beyond the chlorinated ethenes, as oxygenic and low oxygen flux scenarios are relevant to a variety of subsurface biodegradation processes.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.