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Simultaneous Electrochemical and Nuclear Magnetic Resonance Techniques for the Study of Electrochemically Active Biofilms

EMSL Project ID


It is now known that some microbial communities, known as electrochemically active biofilms, have the ability to use solid conducting materials as their terminal electron acceptors for respiration. The details regarding the mechanisms of this extracellular electron transfer are not fully understood, and there is currently significant debate in the literature. For example, it is unclear if biofilms can utilize both conduction-based and diffusion-based electron transfer. If they can, what are the environmental factors that dictate these mechanisms? Furthermore, is it possible to determine the percent of electrons transferred by each mechanism? Existing research tools cannot provide the data needed to address these questions. If we can elucidate the details of the mechanisms and the controlling external conditions then it will be possible to fine-tune and engineer this phenomenon for practical applications, such as bioremediation and alternate energy sources, both of which are of interest to the Department of Energy. We propose to develop a novel NMR reactor capable of simultaneous electrochemical and NMR techniques. This system would allow us to study electrochemically-active biofilms using NMR for the first time. NMR is an ideal tool for biofilm research because it is non-invasive and can measure in situ metabolite concentrations, diffusion coefficients, and spin relaxation rates at the microscale and in multiple dimensions in living biofilms. Using this system we will test our hypothesis that biofilms can use multiple extracellular electron transfer mechanisms concurrently, depending on microenvironment conditions. Our experimental electrochemical and NMR data will be synthesized with theory from multiple disciplines through a suite a mathematical models to predict electron transfer mechanisms under a variety of microenvironment conditions. Ultimately, by coupling the electrochemical, NMR, and modeling techniques with systems biology tools, we will generate the first complete mass and energy balances for Geobacter sulfurreducens and Shewanella oneidensis biofilms. These are the two foremost model electrochemically active biofilm-forming species, each which use a different electron transfer strategy.

The advances generated from this proposed research will place PNNL at the forefront of electrochemically active biofilm research and allow coupled NMR techniques to become a serious tool for biofilm research in general. Beyond addressing our specific questions regarding electron transfer, successful completion of our proposed research will provide a technological advance in NMR that will have numerous other research applications. Examples include research on fuel cells, abiotic/biotic remediation, bioelectricity in animal/plant tissues, biomedical applications, antibiotic penetration, and wound healing.

Project Details

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Principal Investigator

Ryan Renslow
Pacific Northwest National Laboratory

Team Members

Adan Medina
Washington State University