Evidence for a novel mechanism of microbial cellulose degradation

摘要

There are two well studied mechanisms that are used by cellulolytic microorganisms to degrade the cellulose present in plant cell walls and a third less well studied oxidative mechanism used by brown rot fungi. The well studied mechanisms use cellulases to hydrolyze the beta-1,4 linkages present in cellulose, however the way in which cellulases are presented to the environment are quite different for each mechanism. Most aerobic microorganisms secrete a set of cellulases outside the cell (free cellulase mechanism) while most anaerobic microorganisms produce large multi enzyme complexes on their outer surface (cellulosomal mechanism). Their genomic sequences suggest that the aerobic bacterium, Cytophaga hutchinsonii and the anaerobic bacterium, Fibrobacter succinogenes, do not use either of these mechanisms for degrading cellulose, as these organisms only code for normal endocellulases not for processive cellulases like exocellulases and processive endocellulases which are used in both of the well studied mechanisms.