Differential induction of genes related to solvent formation during the shift from acidogenesis to solventogenesis in continuous culture of Clostridium acetobutylicum

The expression of all sequenced acetone and butanol formation genes was followed using mRNA analysis during the shift from acidogenesis to solventogenesis in continuous culture of Clostridium acetobutylicum. Differential induction or derepression of the bdhA, bdhB, and adc genes as well as the sol operon was observed during the pH‐induced shift. The order of induction of the three different butanol dehydrogenase genes was found to be bdhA‐sol operon‐bdhB, offering an explanation for the physiological role of the respective enzymes. Peak mRNA synthesis of an autolysin and a heat shock gene at the onset of solventogenesis was detected in addition to the above‐mentioned genes. None of the hitherto sequenced genes of butanologenic enzymes was found to be involved in butanol production during the Methyl viologen‐induced shift, indicating the presence of yet unknown genes encoding alcohol and aldehyde dehydrogenases.