Clostridium cellulolyticum ATCC 35319 has been extensively studied in the past few years on both the enzymatic and metabolic aspects of cellulose degradation and is considered as the model of mesophilic cellulolytic clostridia. As is true of most cellulolytic clostridia, this bacterium possesses an extracellular multi-enzymatic complex, the cellulosome. Cellulosomes are highly efficient in the degradation of plant cell wall polysaccharides. In C. cellulolyticum, most of the cellulosomal genes are localised in an approximately 26 kb DNA fragment, the cel cluster, where 12 genes have been identified to date cipC-cel48F-cel8C-cel9G-cel9E-orfX-cel9H-cel9J-man5K-cel9M-rgl11Y-cel5N. The C. cellulolyticum cellulosome is organised around the scaffolding protein CipC, which permits the binding of the different cellulosomal enzymes via interactions of dockerin-cohesin domains. Twelve cellulosomal enzymes have been identified including cellulases, hemicellulase and pectinase. The state of knowledge about the structure, ultrastructure, enzymatic activity, regulation and extracellular assembly of the C. cellulolyticum cellulosome are reviewed, and potential biotechnological exploitations discussed. (c) 2005 Elsevier Inc. All rights reserved.