Dynamics of Reductive Dehalogenating Communities Associated with Dehalorespiration Under Conditions of Competition for Hydrogen

四氯乙烯（PCE）和三氯乙烯（TCE）等氯化脂肪烃是美国含水层中含量最多的地下水污染物。虽然通过还原性脱卤微生物对这些污染物进行生物修复在许多地点取得了成功，但仍有许多地点的成功受到限制。这种有限的成功往往是由于缺乏对原位微生物还原脱卤和复杂的生物地球化学过程的了解。麦卡蒂脱盐球菌（dehalococoides mccartyi, Dhc）似乎是将PCE和TCE完全脱氯为无害的乙烯的最重要微生物。作为稀有的、生长缓慢的生物圈的成员，dehalococides sp.是严格的厌氧微生物，对还原性脱卤具有高度的生态位适应性，很难在纯培养中分离出来，并且以未知的方式代谢整合到一个支持的微生物群落中。这项跨学科的工程和科学合作研究将提供对缓慢生长的还原性脱卤微生物的动力学，它们的种群，以及在波动的低浓度氢（它们的首选电子供体）下氯乙烯还原性脱卤过程中相关微生物群落的基本理解。通过实验确定脱卤化群落中不同微生物对氢的竞争的分子和有机体特性以及开发预测数学模型来模拟微生物群落之间对氢的竞争，可以更好地理解这一问题。预期的结果是对自然微生物生态系统中动态变化的各种电子供体和替代电子受体如何引起微生物群落组成和脱卤微生物种群的变化有更深的系统级理解。更广泛的影响。本研究将在三个层面上产生更广泛的影响：1)微生物还原脱卤技术在氯乙烯污染地下水生物修复中的成功工程。跨学科的合作研究将为工程更有效的生物修复系统所需的关键数据和建模提供见解。这种分子/实验、统计和数学相结合的方法预计可用于其他高度优先的环境污染物，如氟烃、重金属或放射性核素的工程补救；2)对Dehalococcoides sp.（生态）生理动态和自然种群结构有了基本的认识，Dehalococcoides sp.是高度生态位适应、稀有、缓慢生长的生物圈成员。研究将使科学家能够开始构建和回答有关这些微生物的生物学和一般低生长条件下的生命的一些关键问题；3)参与本项目的学生将接受微生物生理学和分子方法、分子信息分析的统计方法、环境工程和生物或地球化学系统的数学建模等方面的培训。学生们将学习以工程或微生物学为核心学科的基础知识，并将接受使用统计方法和建模的培训，以培养下一代合作微生物学家和环境工程师。

Chlorinated aliphatic hydrocarbons, such as tetrachloroethene (PCE) and trichloroethene (TCE) are the most abundant groundwater contaminants of US aquifers. While bioremediation of these pollutants via reductively dehalogenating microorganisms has been successful at many sites, there are numerous sites where the success has been limited. This limited success is frequently due to a lack of understanding of in situ microbial reductive dehalogenation and complex biogeochemical processes. Dehalococcoides mccartyi (Dhc) species appear to be the most important microbes for complete dechlorination of PCE and TCE to the harmless ethene. As members of the rare, slow growing biosphere, Dehalococcoides sp. are strictly anaerobic microbes, are highly niche-adapted to reductive dehalogenation, are difficult to isolate in pure culture, and are metabolically integrated in unknown ways into a supporting microbial community. This collaborative, interdisciplinary engineering and science research will provide a fundamental understanding of the dynamics of slow growing, reductively dehalogenating microbes, their populations, and the associated microbial communities during reductive dehalogenation of chloroethenes at fluctuating low concentrations of hydrogen their preferred electron donor. A better understanding will be achieved by a combined approach consisting of experimentally determining molecular and organismal properties of the competition for hydrogen by different microbes of a dehalogenating community and of developing a predictive mathematical model to simulate the competition for hydrogen among the microbial community. The expected outcome is a deeper systems-level understanding of how in a natural microbial ecosystem, dynamically changing diverse electron donors and alternate electron acceptors cause shifts in composition of the microbial community and populations of dehalogenating microbes. Broader Impacts. The broader impacts of this research will be on three levels: 1) Successful engineering of microbial reductive dehalogenation for bioremediation of groundwater contaminated with chloroethenes. The collaborative interdisciplinary research will provide insights into crucial data and modeling needed for engineering more efficient bioremediation systems. This type of combined molecular/experimental, statistical and mathematical approach is expected to be transferable for engineering the remediation of other high priority environmental contaminants, such fluorohydrocarbons, heavy metals, or radionuclides; 2) Fundamental insights will be obtained into the (eco) physiological dynamics and natural population structure of Dehalococcoides sp. which are members of the highly-niche adapted, rare, slow growing biosphere. Studies will enable scientists to begin to frame and answer some crucial questions on the biology of such microbes and on life under low-growth conditions in general; 3) The students involved in this project will be trained in microbial physiology and molecular methods, statistical methods for the analysis of molecular information, in environmental engineering and in mathematical modeling of biological or geochemical systems. The students will learn the fundamentals either in engineering or microbiology as their core discipline, and will also be trained in using statistical methods and modeling to educate the next generation of collaborative microbiologists and environmental engineers.