Functional analysis of the marine cellulolytic system of Saccharophagus degradans

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Saccharophagus degradans 2-40 (Sde2-40) is a marine bacterium with the ability to rapidly degrade 10 different complex polysaccharides (CPs) found in higher plant and algal cell walls. The recently obtained genome sequence has revealed essential elements of the degradative systems for each CP typically found in higher plant cell walls, most notably cellulose. The bacterium is able to grow on Avicel as a sole carbon and energy source, indicating it expresses a true cellulolytic system. Although cellulolytic systems of soil and rumen bacteria and cellulolytic fungi are well characterized, little is known about how cellulose is degraded in the marine environment. The Sde2-40 cellulolytic system appears to be composed of a provocative assemblage of secreted and surface-arrayed enzymes with unique architectures. The structural features of the predicted cellulases and accessory enzymes have been used to assemble a model of the degradation of cellulose by Sde2-40 that has unusual elements. The goal of the proposed studies is to elucidate the mechanism by which 2-40 degrades and processes the cellulose in the marine environment. Biochemical activity of expressed proteins will be used to confirm predicted gene functions and transcriptome analysis employing previously designed microarrays used to establish relative expression levels. Spatial distribution and substrate specificities of functional enzymes will be determined. Gene replacement mutagenesis will be used to evaluate the role of selected enzymes or components. These experiments will allow us to test the role of specific enzymes and estimate fluxes through particular pathways to develop an integrated model for how Sde2-40 degrades cellulose.In addition to the training of undergraduate and graduate students during the course of this research and the gain of knowledge, such as the applications to bioprocessing of cellulosic biomass for bioethanol production, we are involved in two outreach programs designed to introduce and recruit underrepresented minorities into microbiological research. A laboratory module has also been developed for our Microbial Genetics course.