Role of Protistan Predation in TCE Biodegradation

Nancy E.Kinner Proposal编号：CBET-1033127机构：新汉普郡大学标题：原生生物捕食在三氯乙烯生物降解中的作用环境工程从业者面临的最令人困惑的问题之一是三氯乙烯污染地下水站点的生物降解停滞。尽管注入了合适的电子供体和能够将三氯乙烯矿化为二氧化碳的微生物联合体(如KB-1)，但有时氯化溶剂仍然存在。国际地下水协会最近的研究表明，本土地下水原生生物(即2-3微米的纳米鞭毛虫)可以捕食微生物联合体的成员，潜在地阻止它们在原地建立足够的丰度来实现完整的三氯乙烯矿化。拟议的研究将确定原生生物是否以及在什么条件下可以选择性地捕食关键细菌物种，防止该财团完成矿化三氯乙烯及其后代所需的一系列生物降解反应。具体地说，这项研究将确定：(1)原生动物捕食和有机碳的可用性是否对微生物群落结构产生影响；(2)原生生物选择性地捕食TCE降解联合体中的关键物种，如果是，则以什么速率(水中清除细菌/原生生物？h)；(3)在与环境相关的浓度(10-1000微克/L)下，TCE和/或其后代抑制土著原生生物；(4)在被TCE污染的含水层中观察到类似的微生物群落结构变化；以及(5)在其他受TCE污染的地点观察到类似的原生动物分布。这项研究的最终目标是制定策略，以避免捕食对三氯乙烯生物修复的任何不利影响。拟议的研究将使用：(1)微观世界和分子技术；(2)批量喂养实验；(3)经典的蛋白质毒性试验和连续流动非原位扩散箱。PI项目帮助开发了用于研究今天使用的含水层捕食者-猎物关系的主要技术。利用这些资源来研究原生生物对关键细菌物种的捕食是否会扰乱原位TCE生物修复/生物增强的问题，有可能极大地提高我们对地下水生态系统动力学的理解，并提出可能的捕食者避免策略以防止失速(例如，表面联合、改变联合体的细胞表面特征以限制猎物的偏好)。更广泛的影响该项目将培养一名硕士-S学生，并将包括两名本科生助理和最多十名本科生完成与本研究相关的个人项目，以满足他们最高级别的高级项目要求。该项目还将包括最多四名中学生，他们将学习环境工程如何依赖于多学科的科学家团队(微生物学家、水文学家和工程师)，在实验设计、数据分析和解决问题方面相互补充技能和方法。(中学生将包括女孩、西班牙裔和/或非裔美国学生)。这项研究将开发一个关于三氯乙烯污染的地下水含水层的分子数据库，其中将包括真核生物和原核生物。这将作为未来三氯乙烯污染含水层社区图书馆的基础，并将是利用分子技术表征三氯乙烯污染含水层原生生物群落的首批尝试之一。本土微生物和受污染沉积物的来源是位于NH的朴茨茅斯的皮斯国际贸易港(前皮斯空军基地)，这是一个含有三氯乙烯羽状物的裂隙基岩含水层。尽管开发了化学和生物改良剂以促进就地生物修复，但对宝贵的地下水资源的三氯乙烯污染仍然是一个问题。这项建议基于最近关于地下水中普遍存在的自然原生生物的影响的研究结果，旨在解决一些受三氯乙烯污染的含水层停滞不前的可能原因。

ABSTRACTPI: Nancy E. KinnerProposal Number: CBET - 1033127Institution: University of New HampshireTitle: Role of Protistan Predation in TCE BiodegradationIntellectual Merit One of the most perplexing problems facing environmental engineering practitioners is stalls in biodegradation at TCE-contaminated groundwater sites. In spite of injection of a suitable electron donor and a microbial consortium (e.g., KB-1) able to mineralize TCE to CO2, sometimes the chlorinated solvents persist. The PI's recent research has shown that indigenous groundwater protists (i.e., 2-3 ìm nanoflagellates) can prey upon members of the microbial consortia, potentially preventing them from establishing a sufficient abundance in situ to accomplish complete TCE mineralization. The proposed research will determine if, and under what conditions, the protists can selectively prey upon key bacterial species, preventing the consortia from accomplishing the series of biodegradation reactions necessary to mineralize TCE and its progeny. Specifically, the research will determine if: (1) protistan predation and organic carbon availability have an influence on the microbial community structure; (2) protists selectively graze on key species in the TCE-degrading consortia, and if so, at what rates (nL of water cleared of bacteria/protist?h); (3) TCE and/or its progeny, at environmentally-relevant concentrations (10-1000 ìg/L), inhibit indigenous protists; (4) similar changes in the microbial community structure are observed in a TCE-contaminated aquifer; and (5) similar distributions of protists are observed in other TCE-contaminated sites. The ultimate goal of the research is to develop strategies to avoid any adverse effects of predation on TCE bioremediation. The proposed research will be conducted using: (1) microcosms and molecular techniques; (2) batch feeding experiments; (3) classic protistan toxicity tests and continuous flow ex situ diffusion chambers. The project PI has helped to develop the primary techniques used to study aquifer predator-prey relationships that are used today. Bringing these resources to bear on the question of whether protistan predation of key bacterial species can disrupt in situ TCE bioremediation/bioaugmentation has the potential to greatly increase our understanding of groundwater ecosystem dynamics and suggest possible predator avoidance strategies to prevent stalling (e.g., surface association, change in cell surface characteristics of consortia to limit prey preference). Broader Impacts The project will result in the training of one master?s student and will include two undergraduate assistants and up to ten undergraduates completing individual projects related to this research to fulfill their capstone senior project requirement. This project will also include up to four middle-school students who will learn how environmental engineering depends upon multidisciplinary teams of scientists (microbiologists, hydrologists, and engineers) complementing each others skills and approaches to experimental design, data analysis and problem solving. (The middle-schoolers will include girls and Hispanic and/or African-American students). The research will result in the development of a molecular database for TCE-contaminated groundwater aquifers that will include eukaryotes and prokaryotes. This will serve as the foundation for future community libraries for TCE contaminated aquifers, and will represent one of the first attempts to characterize the protistan community in TCE-contaminated aquifers using molecular techniques. The source of the indigenous microbes and contaminated sediments is Pease International Tradeport (Formerly Pease Air Force Base) in Portsmouth, NH, a fractured bedrock aquifer containing a TCE plume. TCE contamination of precious groundwater resources continues to be a problem in spite of development of chemical and biological amendments to stimulate in situ bioremediation. This proposal, building on recent findings regarding the impact of ubiquitous naturally-occurring protists in groundwater, aims to address a likely cause of stalling in some TCE contaminated aquifers.