Elucidating mechanisms for enhanced anaerobic bioremediation in the presence of carbonaceous materials using an integrated material science and molecular microbial ecology approach

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PROJECT SUMMARY: Halogenated compounds, including legacy pollutants (e.g., chlorinated ethenes (CEs), polychlorinated biphenyls) and emerging contaminants (e.g., 1,2,3-trichloropropane), are frequently en- countered at Superfund sites. A common bioremediation strategy for halogenated pollutants in groundwater and sediments is anaerobic reductive dehalogenation by organohalide-respiring bacteria (OHRB). Although effective, OHRB-driven bioremediation strategies are often incomplete in field applications. An emerging reme- diation strategy involving amendment of pyrogenic carbonaceous matter (PCM; e.g., activated carbon (AC)) to the subsurface offers a potential solution to problems with OHRB-driven bioremediation. Recent research high- lights the potential for PCM to promote synergistic interactions among OHRB and the auxiliary microbial com- munity and subsequently improve OHRB-driven bioremediation efficacy. However, the underlying mechanisms of how PCM properties best support microbial network interactions, and thereby enhance OHRB performance and contaminant biodegradation remain unknown. These unknowns limit our ability to optimize OHRB perfor- mance in bioremediation strategies where PCM is used. This proposal is aimed at closing the knowledge gap concerning specific surface effects of PCM on the performance of pollutant-degrading microorganisms, espe- cially OHRB. The central hypothesis is that key PCM properties will shape microbial community structure and drive the expression of metabolic functions associated with reductive dehalogenation processes. Elucidat- ing positive impacts between PCM and OHRB will allow for the development of tailored PCM that foster syner- gistic microbial network interactions and facilitate more effective and sustainable bioremediation. The hypothe- sis is based on preliminary data showing that OHRB-driven CE biotransformation performance was improved in the presence of biochar, OHRB were attached to carbon surfaces, and that PCM-like tunable polymer net- works can be successfully synthesized. Guided by these preliminary data, we will test the hypothesis by 1) providing a tunable platform for synthesis of PCM-like polymer membranes where surface charge and redox- active properties are varied individually, 2) quantifying the effects of PCM surface properties on microbial net- work interactions and subsequent performance of an organohalide-respiring mixed culture and, 3) developing tailored PCM for enhanced anaerobic bioremediation and contaminant mixture retention and validating material performance in microcosms. The proposed research is innovative because we will use a tunable platform to change material surface properties and employ advanced molecular microbial ecology tools to assess the im- pacts of these properties on microbial community structure, function, and activity including OHRB. Outcomes of this project will benefit human health and realize economic benefits by reducing human exposure to halo- genated pollutants in the environment and demonstrating the potential for more effective and sustainable re- mediation approaches that combine tailored PCM and OHRB.