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Project Progress

Hydrogenotrophic methanogenesis occurs in a variety of anaerobic habitats, may have played an important role on early earth, and could be a dominant metabolism on other planetary bodies. In the past year we published our genome sequence of Methanoccoccus maripaludis, a model species of hydrogenotrophic methanogen. We also published on an advance in genetic methodology for M. maripaludis, and on a study of lateral gene transfer that gave rise to the unusual ability this species to use alanine as a nitrogen source for growth. We have made considerable progress in the post-genomics of M. maripaludis. Thus, we have used chemostat-grown cultures and expression arrays to learn how M. maripaludis responds to conditions in which growth is limited by the supply of hydrogen, an important electron donor in methanogenesis. We will continue these studies in the coming year and submit a paper for publication. We have also made progress in using genetics to understand the mechanism of methanogenesis. We have made mutants that are deficient in enzymes that catalyze steps in methanogenesis. We plan to make additional mutations that will allow us to elucidate the roles of certain enzymes in electron flow and in methanogenesis from the alternative substrate, formate. These metabolic studies will add to our understanding of a pathway that produces methane and that could have played fundamental roles in early life on earth. Finally, we have collaborated with D. Stahl to generate preliminary data regarding the patterns of gene expression in M. maripaludis and in Desulfovibrio sp. that result from the co-culture of the two species. We have formulated plans with the Stahl lab to generate additional samples of M. maripaludis monocultures grown in a chemostat for use in the gene expression analysis. The continuation of this project will take place in the coming year.