Dynamics and control of the clostridium acetobutylicum metabolic network

Clostridium acetobutylicum is an anaerobic, Gram-positive, spore forming bacteria that is characterized by its unique two-step metabolic pathway. Upon growth in presence of carbon sources, the bacterium first consumes them to produce organic acids in a phase that is known as acidogenesis. Upon accumulation of acids, the organism shuts down acid production, and in fact, consumes the acids to convert them into organic solvents (acetone, butanol, and ethanol). The second phase is called solventogenesis. In this study, using both experimental and computational techniques, we explore the dynamics of the Clostridium metabolic network, and more specifically, the switch from acidogenesis to solventogenesis. Our results show that the two phases are expressed independently of each other, and not in a switch-like manner. We also demonstrate that within each of the two phases, there exists a hierarchy of expression of acids and solvents. We also report presence of negative feedback loops in the network leading to a more complex picture of the Clostridium metabolic network.