Lawrence Berkeley National Laboratory

Thermobifida fusca is a moderately thermophilic soil bacterium that belongs to Actinobacteria. 3 It is a major degrader of plant cell walls and has been used as a model organism for the study of 4 secreted, thermostable cellulases. The complete genome sequence showed that T. fusca has a 5 single circular chromosome of 3642249 bp predicted to encode 3117 proteins and 65 RNA6 species with a coding density of 85 percent. Genome analysis revealed the existence of 29 putative 7 glycoside hydrolases in addition to the previously identified cellulases and xylanases. The 8 glycosyl hydrolases include enzymes predicted to exhibit mainly dextran/starch and xylan 9 degrading functions. T. fusca possesses two protein secretion systems: the sec general secretion 10 system and the twin-arginine translocation system. Several of the secreted cellulases have 11 sequence signatures indicating their secretion may be mediated by the twin-arginine12 translocation system. T. fusca has extensive transport systems for import of carbohydrates 13 coupled to transcriptional regulators controlling the expression of the transporters and14 glycosylhydrolases. In addition to providing an overview of the physiology of a soil 15 actinomycete, this study presents insights on the transcriptional regulation and secretion of16 cellulases which may facilitate the industrial exploitation of these systems.