STARTER GRANT: Characterization of Catabolic Pathways for the Degradation of Plant-related Aromatics in the Marine Bacterium Silicibacter Pomeroyi

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The remineralization of the aromatic polymer lignin and its related compounds is critical to the global carbon cycle, yet little is known of the natural communities and the processes involved. The coastal salt marshes of the southeastern U.S. are heavily influenced by lignin-related compounds of local and allochthonous origins, and are ideal sites for investigations of catabolic pathways that are harbored within decomposer communities. Members of one lineage of marine bacteria, the Roseobacter clade, are particularly well-suited for such studies as they are abundant in these coastal salt marshes and are hypothesized to be responsible for a significant fraction of aromatic compound degradation in these systems. This project focuses on Roseobacter isolate Silicibacter pomeroyi and uses genome data, physiological growth studies, and gene expression levels to better understand the catabolic processes and regulatory networks mediating the transformation of the monomeric constituents of lignin by members of this group.The genome sequence of S. pomeroyi reveals the presence of three, potentially competing, pathways for the degradation of plant-related aromatic compounds. The aims are to: (i) Identify lignin-related compounds that can be utilized by S. pomeroyi as primary growth substrates, (ii) identify which of the three pathways, pca, gentisate, or boxA, will catabolizable substrates, and iii. utitlize molecular approaches to monitor gene expression levels of key enzymes of the three pathways. Detailed characterizations of the catabolic properties of S. pomeroyi will provide the critical foundation needed to understand how naturally-occurring aromatic compounds are processed by members of the Roseobacter lineage in the environment.This project will have broad impact through its contribution toward the elucidation of metabolic networks that govern processes central to the biogeochemical cycling of carbon. Moreover, it will support training opportunities for one graduate student and two undergraduate students.