Genomic and physiological analyses reveal that extremely thermophilicCaldicellulosiruptor changbaiensisdeploys unique cellulose attachment mechanisms

Abstract

ABSTRACTThe genusCaldicellulosiruptorare extremely thermophilic, heterotrophic anaerobes that degrade plant biomass using modular, multifunctional enzymes. Prior pangenome analyses determined that this genus is genetically diverse, with the current pangenome remaining open, meaning that new genes are expected with each additional genome sequence added. Given the high biodiversity observed among the genusCaldicellulosiruptor, we have sequenced and added a 14thspecies,Caldicellulosiruptor changbaiensis, to the pangenome. The pangenome now includes 3,791 ortholog clusters, 120 of which are unique toC. changbaiensisand may be involved in plant biomass degradation. Comparisons betweenC. changbaiensisandCaldicellulosiruptor besciion the basis of growth kinetics, cellulose solubilization and cell attachment to polysaccharides highlighted physiological differences between the two species which are supported by their respective gene inventories. Most significantly, these comparisons indicated thatC. changbaiensispossesses unique cellulose attachment mechanisms not observed among the other strongly cellulolytic members of the genusCaldicellulosiruptor.