Genetic Regulation of the Cellulosome In Clostridium Acetobutylicum

The engineering of a microorganism to produce advanced biofuels in a consolidated bioprocess remains an important challenge. The bacterium Clostridium acetobutylicum ATCC 824 is an industrial organism that undergoes acetone, biobutanol, and ethanol (ABE) fermentation. While C. acetobutylicum is able to produce biobutanol from both hexose and pentose sugars, it is unable to utilize cellulose due to the lack of a functional cellulosome, an extracellular multi-enzyme complex containing functional cellulase enzymes.  C. acetobutylicum contains genes that encode for a potentially effective cellulosome, but this cellulosomal operon remains transcriptionally repressed, even in the presence of cellulose.  Several research groups have presented hypotheses regarding the repression of the cellulosome in C. acetobutylicum.  Here, we use a combinatorial sampling of the cellulosome promoter region as a method to determine location of potential repressor binding.  These are then compared to computational predictions of repressor binding in this promoter region. The results of this research have provided extensive insight into the regulatory mechanisms responsible for suppressing the cellulosome in this highly solventogenic industrial bacterium. The results presented here are currently being used to design effective metabolic engineering strategies.