Comparative analysis on the membrane proteome of Clostridium acetobutylicum wild type strain and its butanol-tolerant mutant

The solventogenic bacterium Clostridium acetobutylicum is the most important species of Clostridium used in the fermentation industry. However, the intolerance to butanol hampers the efficient production of solvents. Butanol toxicity has been attributed to the chaotropic effect on the cell membrane, but the knowledge on the effect of butanol on membrane associated proteins is quite limited. Using 2-DE combined with MALDI-TOF MS/MS and 1-DE integrated with LC-MS/MS, 341 proteins in the membrane fractions of cell lysate were identified, thus establishing the first comprehensive membrane proteome of C. acetobutylicum. The identified proteins are mainly involved in transport, cellular membrane/wall machinery, formation of surface coat and flagella, and energy metabolism. Comparative analysis on the membrane proteomes of the wild type strain DSM 1731 and its butanol-tolerant mutant Rh8 revealed 73 differentially expressed proteins. Hierarchical clustering analysis suggested that mutant Rh8 may have evolved a more stabilized membrane structure, and have developed a cost-efficient energy metabolism strategy, to cope with the butanol challenge. This comparative membrane proteomics study, together with our previous published work on comparative cytoplasmic proteomics, allows us to obtain a systemic understanding of the effect of butanol on cellular physiology of C. acetobutylicum.