N-145. Assessing Power Production and Microbial Ecology of Environmental Marine Microbial Fuel Cells

H. K. White1, C. E. Reimers2, M. Nielsen2, S. Sharma1, P. R. Girguis1;
1Harvard Univ., Cambridge, MA, 2Oregon State Univ., Corvallis, OR.

Microbial fuel cells (MFCs) are devices that generate electricity directly from microbial metabolism. Typically when MFCs are deployed in natural settings, e.g. the seafloor, anodes are placed in anoxic milieus (e.g. sediments) while the cathodes reside in oxic seawater. Microbes that colonize the MFCs may be involved in power production, via organic matter oxidation directly coupled by electron transfer to the anode, or via syntrophic associations that yield intermediate chemical electron donors. Here we focus on a MFC deployed over a cold seep in the Monterey Canyon, California, and compare it to a number of different marine MFCs including systems deployed with anodes placed within a hydrothermal vent chimney, or within organic-rich coastal marine sediments, as well as plankton-fueled laboratory MFCs. Power densities, microbial diversity of anodic and cathodic communities, and quantification of dominant phylotypes by real-time quantitative PCR (qPCR) are compared between the MFCs and to the geochemistry of their surrounding environment. Similar phylotypes are observed between MFCs deployed in these diverse marine environments and include alpha-, delta-, epsilon- and gamma-proteobacteria, as well as the Flavobacterium-Cytophaga-Bacteroides (FCB). Predictable relationships between geochemistry (such as organic carbon and sulfide concentrations), power production and microbial ecology of these MFCs are also observed. These data enable us to better determine the role of key microbial phylotypes and their capacity to contribute to power production in a MFC.