Transcriptional regulation of solventogenesis in Clostridium acetobutylicum.

Solvent synthesis in Clostridium acetobutylicum is induced in concert with sporulation to counteract the dangerous effects of produced butyric and acetic acids and to provide the cell with sufficient time to complete endospore formation. Cardinal transcription units for butanol and acetone production are the sol and adc operons encoding butyraldehyde/butanol dehydrogenase and coenzyme A transferase as well as acetoacetate decarboxylase. Induction is achieved by a decreased level of DNA supercoiling and the transcription factor Spo0A, possibly in cooperation with other regulatory proteins. A number of other operons is also turned on during this metabolic switch, whose physiological relevance, however, is only partly understood. The recent completion of C. acetobutylicum genome sequencing will pave the way for transcriptional profiling and thus allow comprehension of the coherent regulatory networks of solventogenesis and sporulation.