Genome of a Cellulose-Eating Bacterium Sequenced

The bacterium Clostridium thermocellum and a handful of close relatives are the only organisms known to break down one of the hardest materials in nature – the cellulose found in trees and tough, woody plants. This unique ability could be quite valuable: Scientists are working to adapt it to recycling cellulose-based waste and producing biofuel. Now, some 50 years after it was identified and 30 years after the discovery of the cellular organelle that enables it to digest cellulose, the genome of a particularly efficient strain of this bacterium has been sequenced, along with that of a mutant strain used in research. The genome was announced in the Journal of Bacteriology.

Profs. Ed Bayer of the Weizmann Institute’s Biological Chemistry Department and Raphael Lamed of Tel Aviv University were the first to discover the cellulose-digesting mechanism in Clostridium thermocellum. This mechanism, an organelle they named the cellulosome, breaks the long, sturdy chains of sugars in cellulose molecules into shorter, soluble sugars. Their finding was based on a mutant strain they created in the lab that enabled them to isolate the structures. In the 30 years since that discovery, Bayer and Lamed have made steady progress elucidating exactly how the cellulosome works, as well as creating new versions that are more efficient and function in different conditions. “At this point,” says Bayer, “we can take the cellulosome apart and put it back together again like Lego. But until a year or two ago, the idea of getting a complete sequence of the strain we have been working with, known as YS, was just a dream.”