PNNL

Abstract

Stimulated by acetate-amendment field experiments conducted in 2007 and 2008, anaerobic microbial populations in the aquifer at the Rifle Integrated Field Research Challenge site in Colorado reduced mobile U(VI) to insoluble U(IV). During this period, planktonic biomass was sampled at various time points and used to quantitatively evaluate proteomes, both spatially and temporally to study the dynamics of the microbial community proteome dynamics in relationship to geochemical measurements. As there were no comprehensive genome sequence data available at the time, we systematically evaluated different organisms to generate a "pseudo-metagenome" for proteomics analyses. Proteomics results supported the dominance of Geobacteraceae during biostimulation and revealed a shift from iron reduction to sulfate reduction, evidenced by changes in community membership. Because U(VI) is reduced at a lower rate during sulfate reduction, detecting this shift is important to maintaining the maximum rate of U(VI) reduction. In addition, the comparison of proteome measurements made at the end of the 2007 field experiment to the 2008 field experiment revealed a modified community structure. Importantly, the failure of a community to rebound following the cessation of biostimulation needs to be included in long-term remediation strategies.