In situ electrochemical characterization of bioremediation microbial processes

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My research program uses in situ sensor measurements to characterize and monitor microbial processes of environmental significance. Microbial processes control environmental geochemistry everywhere on Earth, and microbes perform critical functions in sequestering and remediating many types of environmental contaminants. Lithotrophic bacteria-those that use inorganic metabolic substrates such as Fe, S, and N-are particularly important in bioremediation, because they drive biogeochemical reactions that can attenuate, transform, or release contaminants such as Mn, As, and Hg. Their importance makes detailed and nuanced understanding of how lithotrophic microbes cycle inorganic metabolic substrates critical to effective bioremediation strategies. This research approach provides previously inaccessible information about the fundamental aspects of geochemical cycling and energy transduction in complex natural microbial communities. Electrodes are often used to monitor microbially-relevant geochemical parameters in environmental systems, including pH, oxidation-reduction potential, conductivity, dissolved oxygen, temperature, and concentrations of dissolved ions (i.e., ammonia, hydrogen sulfide). My recent work indicates that, in addition to recording the real-time physicochemical environment, electrodes record previously inaccessible information about ongoing dynamic biogeochemical processes. Electrode time series record real-time microbial mediation of the motion of metabolic substrates. Fractal analysis of these time series shows that time series arising from different geochemical pathways of the same biogeochemical reaction have characteristic, different fractal dimensions. This distinguishes biological and abiotic contributions to ongoing biogeochemical processes. The short-term goals of my research program are to characterize lithotrophic metabolic pathways of bioremediation interest, including Fe- and As-oxidation (acid mine drainage), Mn-oxidation (Fredericton municipal drinking water), and cyanobacterial (photosynthetic) toxin production (microcystin and anatoxin in surface water bodies). This will be accomplished with lab-based microcosm experiments. The long-term goal, building on the study of individual pathways, is the application of these methods to natural (pristine and contaminated) microbial communities. The capability to distinguish and measure biogeochemical reactions simultaneously in situ represents a major innovation on existing efforts to develop low-cost sensor-based environmental monitoring strategies, as well as extending well-established bioelectrical remediation methods to collect more information about the functions of bioremediation microbial communities. Using sensors to obtain process-specific biogeochemical information reduces the need for in-person monitoring of sites, as well as providing better spatially and temporally resolved data to constrain biogeochemical processes.