Role of Protistan Predation in TCE Biodegradation

University Of New Hampshire, Durham NH

Investigators

Abstract

ABSTRACT PI: Nancy E. Kinner Proposal Number: CBET - 1033127 Institution: University of New Hampshire Title: Role of Protistan Predation in TCE Biodegradation Intellectual 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.