Bacterial genomes: what they teach us about cellulose degradation

Genome sequencing of cellulolytic bacteria combined with analyses using structural and sequence similarity software reveals potential cellulolytic enzymes not previously recovered by routine purification or shotgun cloning techniques. Comparison of the presence and absence of potential cellulases across the prokaryotes indicate that there are at least four distinct mechanisms of cellulose degradation; two distinct soluble systems and two separate cell-based systems can be postulated. None of the mechanisms appear completely homologous to the Trichoderma system of cellulose degradation. Minimum sets of bacterial cellulases can be predicted for the soluble sets based on comparison across genomes, leading to testable hypotheses on cellulose degradation.