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Journal of Bacteriology, October 2008, p. 6559-6567, Vol. 190, No. 20
0021-9193/08/$08.00+0     doi:10.1128/JB.00574-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Two-Component System PhoPR of Clostridium acetobutylicum Is Involved in Phosphate-Dependent Gene Regulation {triangledown}

Tomas Fiedler,1,{dagger} Maren Mix,1,{ddagger} Uta Meyer,1,§ Stefan Mikkat,2 Michael O. Glocker,2 Hubert Bahl,1 and Ralf-Jörg Fischer1*

Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Straße 3, D-18051 Rostock, Germany,1 Proteome Center Rostock, Medical Faculty, University of Rostock, Schillingallee 69, D-18057 Rostock, Germany2

Received 25 April 2008/ Accepted 30 July 2008

The phoPR gene locus of Clostridium acetobutylicum ATCC 824 comprises two genes, phoP and phoR. Deduced proteins are predicted to represent a response regulator and sensor kinase of a phosphate-dependent two-component regulatory system. We analyzed the expression patterns of phoPR in Pi-limited chemostat cultures and in response to Pi pulses. A basic transcription level under high-phosphate conditions was shown, and a significant increase in mRNA transcript levels was found when external Pi concentrations dropped below 0.3 mM. In two-dimensional gel electrophoresis experiments, a 2.5-fold increase in PhoP was observed under Pi-limiting growth conditions compared to growth with an excess of Pi. At least three different transcription start points for phoP were determined by primer extension analyses. Proteins PhoP and an N-terminally truncated *PhoR were individually expressed heterologously in Escherichia coli and purified. Autophosphorylation of *PhoR and phosphorylation of PhoP were shown in vitro. Electromobility shift assays proved that there was a specific binding of PhoP to the promoter region of the phosphate-regulated pst operon of C. acetobutylicum.

* Corresponding author. Mailing address: University of Rostock, Institute of Biological Sciences, Division of Microbiology, Albert-Einstein-Straße 3, D-18051 Rostock, Germany. Phone: 49-381-498-6153. Fax: 49-381-498-6152. E-mail: ralf-joerg.fischer{at}uni-rostock.de

{triangledown} Published ahead of print on 8 August 2008.

{dagger} Present address: University of Rostock, Medical Faculty, Institute of Med. Microbiology, Virology and Hygiene, Schillingallee 70, D-18057 Rostock, Germany.

{ddagger} Present address: University of Rostock, Institute of Chemistry, Divison of Analytical, Technical and Environmental Chemistry, Dr.-Lorenz-Weg 1, D-18051 Rostock, Germany.

§ Present address: Sanofi-Aventis Deutschland GmbH, Frankfurt Biotechnology, Industriepark Höchst, Building D710, D-65926 Frankfurt am Main, Germany.

Journal of Bacteriology, October 2008, p. 6559-6567, Vol. 190, No. 20
0021-9193/08/$08.00+0     doi:10.1128/JB.00574-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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