Genome Sequence and Analysis of the Soil Cellulolytic ActinomyceteThermobifida fuscaYX

Abstract

Thermobifida fusca is a moderately thermophilic soil bacterium that belongs to Actinobacteria. It is a major degrader of plant cell walls and has been used as a model organism for the study of secreted, thermostable cellulases. The complete genome sequence showed that T. fusca has a single circular chromosome of 3,642,249 bp predicted to encode 3,117 proteins and 65 RNA species with a coding density of 85%. Genome analysis revealed the existence of 29 putative glycoside hydrolases in addition to the previously identified cellulases and xylanases. The glycosyl hydrolases include enzymes predicted to exhibit mainly dextran/starch-and xylan-degrading functions. T. fusca possesses two protein secretion systems: the sec general secretion system and the twin-arginine translocation system. Several of the secreted cellulases have sequence signatures indicating their secretion may be mediated by the twin-arginine translocation system. T. fusca has extensive transport systems for import of carbohydrates coupled to transcriptional regulators controlling the expression of the transporters and glycosylhydrolases. In addition to providing an overview of the physiology of a soil actinomycete, this study presents insights on the transcriptional regulation and secretion of cellulases which may facilitate the industrial exploitation of these systems.

Structural insights into a unique cellulase fold and mechanism of cellulose hydrolysis

“…Thus, CBMs belonging to families 4, 17, and 28 recognize distinct amorphous or paracrystalline regions of cellulose (24,25), and CBM2a, CBM3a, and CBM1, which bind to crystalline cellulose, also display distinct specificities (26). Many cellulose-degrading bacteria express a large number of endo-β-1,4-glucanases (27,28), exemplified by C. thermocellum that has the potential to synthesize approximately 30 endoglucanases. The biological rationale for the expansion in this enzyme activity in C. thermocellum and other organisms is currently unclear.…”

Laboratory Evolution and Multi-platform Genome Re-sequencing of the Cellulolytic Actinobacterium Thermobifida fusca

“…Adaptive Evolution of T. fusca-Starting with the wild-type strain of T. fusca whose genome has recently been sequenced (8), laboratory evolution experiments were conducted for growth in two conditions (both at 55°C): 40 days on Hagerdahl medium with 0.1% cellobiose (31) or 40 days on Hagerdahl medium where the carbon source was alternately switched every day between 0.1% cellobiose or 0.1% glucose. Two different evolved strains of T. fusca (mutant grown on cellobiose, muC 2 and mutant grown by switching sugars, muS) were generated by serial passage of cells into fresh medium (9) while cells remained in exponential growth.…”

“…While generally poorly characterized, cellulolytic microbes possess great physiological and biochemical diversity making them interesting organisms to study from both a basic and applied perspective. Thermobifida fusca is a particularly interesting cellulolytic actinobacterium that is aerobic, thermophilic (8), and is more efficient at producing cellulases than most anaerobic cellulolytic bacteria (5).…”

Structure elucidation and biosynthesis of fuscachelins, peptide siderophores from the moderate thermophile Thermobifida fusca

“…The genomic sequence of T. fusca YX was reported recently (21). There are no characterized secondary metabolites from this actinomycete and few characterized natural products from any thermophilic bacteria or archaea (22).…”