DIFFERENTIAL INDUCTION OF GENES RELATED TO SOLVENT FORMATION DURING THE SHIFT FROM ACIDOGENESIS TO SOLVENTOGENESIS IN CONTINUOUS-CULTURE OFCLOSTRIDIUM-ACETOBUTYLICUM

The expression of all sequenced acetone and butanol formation genes wa s followed using mRNA analysis during the shift from acidogenesis to s olventogenesis in continuous culture of Clostridium acetobutylicum. Di fferential induction or derepression of the bdhA, bdhB, and ade genes as well as the sol operon was observed during the pH-induced shift. Th e order of induction of the three different butanol dehydrogenase gene s was found to be bdhA-sol operon-bdhB, offering an explanation for th e physiological role of the respective enzymes. Peak mRNA synthesis of an autolysin and a heat shock gene at the onset of solventogenesis wa s detected in addition to the above-mentioned genes. None of the hithe rto sequenced genes of butanologenic enzymes was found to be involved in butanol production during the Methyl viologen-induced shift, indica ting the presence of yet unknown genes encoding alcohol and aldehyde d ehydrogenases.