Role of quorum sensing in the regulation of butanol formation and sporulation in Clostridium beijerinckii

Several members of the genus Clostridium are well known for their ability to convert sugars and starches into organic acids and solvents. During the first half of the last century, these bacteria were used for the large scale production of acetone and butanol, but today the classical AB (acetone-butanol) fermentation process is no longer economically viable. Thus, considerable efforts have been devoted to improving the organisms' performance through metabolic engineering. However, decisive breakthroughs are yet to be made. A major reason for this is our limited understanding of the organisms' physiology and metabolism, including the mechanisms that govern timing and extent of solvent formation.

In previous DTP projects, we discovered a large number of quorum sensing systems in solvent-producing clostridia, which enable individual cells of a population to communicate with one another via diffusible signal molecules. We have shown that many of these systems strongly influence the production acetone, butanol and ethanol, but the underlying molecular mechanisms remain unknown. However, a thorough understanding of the physiological factors and regulatory mechanisms constraining solvent formation is a prerequisite for successful metabolic engineering of the respective species.

Using an established industrial strain of Clostridium beijerinckii, the specific aims of this study are to (i) establish the transcriptional, translational, and physiological changes occurring in a quorum sensing-deficient mutant; (ii) identify the genes directly regulated by the quorum sensing regulator; (iii) exploit this knowledge for the generation of strains in which solvent formation can be maximised by earlier or higher expression of the genes involved.