This project is funded through the US Air Force, with Dr. David Barber of Vet Med as PI. Microbial communities in sediments underpin many of the biogeochemical cycles that drive ecosystem function and make significant contributions to the chemistry of the water column, such that interactions between sediment microbial communities and nanomaterials should be considered. The potential impacts of nanomaterials on microbial community function, and subsequent interactions with other biota in an ecosystem, will likely depend on the nature of the nanomaterial. Depending on the chemistries and relative toxicities of the nanomaterial, individual biogeochemical cycles may be disrupted or major pathways within those cycles may be altered, which could in turn affect either the bioavailability and transport of the nanomaterial, or the activity of the nanomaterial, or both.

Decomposition of plant material in sediments involves a succession of functional groups of microorganisms responsible for breakdown of cellulose in smaller molecules, fermentation of monosaccharides to volatile fatty acids and alcohols, and the eventual consumption of those fermentation products by methanogens and sulfate reducing bacteria. We propose to use a tiered approach to investigate potential impacts of selected nanomaterials on the flow of carbon and electrons in laboratory microcosms. Community level physiological profiling (Garland et al., 2003; Vaisanen et al., 2005) will be used to investigate the potential impacts of nanomaterials on the range of substrates used as sole carbon sources by the microbial community. Methanogenesis and sulfate reduction rates will be measured with a range of electron donors (Chauhan et al., 2004; Castro et al., 2004). If one particular metabolic pathway (e.g., sulfate reduction via acetate) is shown to be sensitive to the presence of nanoparticles, potential shifts in community structure will be evaluated by cloning and sequence analysis of the appropriate gene (Castro et al., 2002, 2004).