MICROBIAL DIVERSITY 2009 Methanogenic communities and methanogenesis in the rhizoplanes of wetland plants MICROBIAL DIVERSITY 2009

Wetlands are the largest natural source of methane (CH4), a potent greenhouse gas. The microbial communities living on the surfaces of plants within wetlands are still poorly characterized. Both rates of methanogenesis and methanogenic community composition were examined in 3 different wetland sites in Cape Cod, Massachusetts. Sites included an acidic swamp (pH=4.8), a cranberry bog (pH = 6.0), and a saltwater march (pH = 7.0). Plants chosen for the study were dominant at each respective location. The swamp roots showed the most CH4 production over a two week period at 2.1 ± 0.2 mmol L-1 compared to 0.61 ± 0.2 mmol L-1 for the bog roots and negligible amounts for the marsh. Roots showed a higher amount of CH4 production than the sediment from the swamp whereas the sediment generated more CH4 than the roots within the bog. Clone libraries showed a dominance of Methanosarcinales for the swamp and Methanobacteriales for the bog. T-RFLP analysis also showed the presence of several methanogenic clusters including group E2, RC-III, and Methanobacteriales in the bog and Rice cluster-I and Methanosaetaceae in the swamp. No methanogens were found in the marsh through molecular techniques. Results display a varying interaction of methanogens with plant roots, but yield strong evidence of methanogenic communities living in association with plant roots in wetland areas