title: Genome-wide gene expression analysis of the switch between acidogenesis and solventogenesis in continuous cultures of Clostridium acetobutylicum.
abstract: Clostridium acetobutylicum is able to switch from acidogenic growth to solventogenic growth. We used phosphate-limited continuous cultures that established acidogenic growth at pH 5.8 and solventogenic growth at pH 4.5. These cultures allowed a detailed transcriptomic study of the switch from acidogenesis to solventogenesis that is not superimposed by sporulation and other growth phase-dependent parameters. These experiments led to new insights into the physiological role of several genes involved in solvent formation. The adc gene for acetone decarboxylase is upregulated well before the rest of the sol locus during the switch, and pyruvate decarboxylase is induced exclusively for the period of this switch. The aldehyde-alcohol dehydrogenase gene adhE1 located in the sol operon is regulated antagonistically to the paralog adhE2 that is expressed during acidogenic conditions. A similar antagonistic pattern can be seen with the two paralogs of thiolase genes, thlA and thlB. Interestingly, the genes coding for the putative cellulosome in C. acetobutylicum are exclusively transcribed throughout solventogenic growth. The genes for stress response are only induced during the shift but not in the course of solventogenesis when butanol is present in the culture. Finally, the data clearly indicate that solventogenesis is independent from sporulation.
authors.affiliation: Abteilung für Genomische und Angewandte Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Göttingen, Deutschland.
authors.forename: Christina
authors.initials: C
authors.lastname: Grimmler
authors.forename: Holger
authors.initials: H
authors.lastname: Janssen
authors.forename: Desireé
authors.initials: D
authors.lastname: Krausse
authors.forename: Ralf-Jörg
authors.initials: RJ
authors.lastname: Fischer
authors.forename: Hubert
authors.initials: H
authors.lastname: Bahl
authors.forename: Peter
authors.initials: P
authors.lastname: Dürre
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Liebl
authors.forename: Armin
authors.initials: A
authors.lastname: Ehrenreich
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism; D000440:Butanols / Q000378:metabolism; D002264:Carboxylic Acids / Q000378:metabolism*; D044603:Cellulosomes / Q000378:metabolism; D046969:Clostridium acetobutylicum / Q000235:genetics* / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D053858:Metabolic Networks and Pathways / Q000235:genetics; D046228:Microarray Analysis; D011767:Pyruvate Decarboxylase / Q000378:metabolism; D012997:Solvents / Q000378:metabolism*
chemical_list: D000440:Butanols; D002264:Carboxylic Acids; D003470:Culture Media; D012997:Solvents; D000426:Alcohol Dehydrogenase; D011767:Pyruvate Decarboxylase