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Journal of Bacteriology, October 2009, p. 6082-6093, Vol. 191, No. 19
0021-9193/09/$08.00+0     doi:10.1128/JB.00351-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The Role of PerR in O2-Affected Gene Expression of Clostridium acetobutylicum{triangledown} ,{dagger}

Falk Hillmann,1 Christina Döring,2 Oliver Riebe,1 Armin Ehrenreich,2,{ddagger} Ralf-Jörg Fischer,1 and Hubert Bahl1*

Abteilung Mikrobiologie, Institut für Biowissenschaften, Universität Rostock, Albert Einstein Str. 3, D-18051 Rostock, Germany,1 Abteilung Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany2

Received 13 March 2009/ Accepted 9 July 2009

In the strict anaerobe Clostridium acetobutylicum, a PerR-homologous protein has recently been identified as being a key repressor of a reductive machinery for the scavenging of reactive oxygen species and molecular O2. In the absence of PerR, the full derepression of its regulon resulted in increased resistance to oxidative stress and nearly full tolerance of an aerobic environment. In the present study, the complementation of a Bacillus subtilis PerR mutant confirmed that the homologous protein from C. acetobutylicum acts as a functional peroxide sensor in vivo. Furthermore, we used a transcriptomic approach to analyze gene expression in the aerotolerant PerR mutant strain and compared it to the O2 stimulon of wild-type C. acetobutylicum. The genes encoding the components of the alternative detoxification system were PerR regulated. Only few other targets of direct PerR regulation were identified, including two highly expressed genes encoding enzymes that are putatively involved in the central energy metabolism. All of them were highly induced when wild-type cells were exposed to sublethal levels of O2. Under these conditions, C. acetobutylicum also activated the repair and biogenesis of DNA and Fe-S clusters as well as the transcription of a gene encoding an unknown CO dehydrogenase-like enzyme. Surprisingly few genes were downregulated when exposed to O2, including those involved in butyrate formation. In summary, these results show that the defense of this strict anaerobe against oxidative stress is robust and by far not limited to the removal of O2 and its reactive derivatives.

* Corresponding author. Mailing address: Abt. Mikrobiologie, Institut für Biowissenschaften, Universität Rostock, Albert Einstein Str. 3, D-18051 Rostock, Germany. Phone: 49-381-498-6150. Fax: 49-381-498-6152. E-mail: hubert.bahl{at}uni-rostock.de

{triangledown} Published ahead of print on 31 July 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Present address: Lehrstuhl für Mikrobiologie, Technische Universität München, Am Hochanger 4, 85350 Freising, Germany.

Journal of Bacteriology, October 2009, p. 6082-6093, Vol. 191, No. 19
0021-9193/09/$08.00+0     doi:10.1128/JB.00351-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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