Tuesday, July 26, 2011: 3:00 PM
Nottoway, 4th fl (Sheraton New Orleans)
Microbial communities in the wet tropical forest soils of Puerto Rico are responsible for near complete decomposition of leaf plant litter under anaerobic conditions, or conditions of fluctuating redox (with cycles of hours to days). To explore this, we cultivated feedstock-adapted anaerobic consortia (FACs) derived from Puerto Rico forest soils in two forest types: short cloud forest (SCF) soils are perennially soaked, while Bisley Ridge soils (BisR) are more iron-rich and experience fluctuating redox. Communities were anaerobically passed through a succession of four transfers in minimal media with switchgrass as the sole carbon source, then amended with the terminal electron acceptors nitrate, sulfate, or iron to examine the effect on switchgrass deconstruction. Based on methane and carbon dioxide production rates, nitrate and iron caused an increase in C mineralization in BisR-FACs, while switchgrass alone had the highest C mineralization in SCF-FACs. Specific enzyme activity rates were higher overall in SCF-FACs compared to BisR-FACs. Microbial community profiling of the small subunit ribosomal RNA gene revealed Actinobacteria and Gammaproteobacteria as dominant organisms. Metagenomic analysis was performed on BisR-FACs from switchgrass only and iron-amended microcosms, revealing increased richness in the iron-amended FAC (324 taxa) compared to the unamended (81 taxa), as well as a different distribution of cellulases and liginases in each. Bacteria likely play a strong role in decomposition in anaerobic soils, which makes them attractive for application to microbial engineering of biofuels producers, as well as providing potential solutions to the lignin problem.