This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fischer, R.-J. Articles by Bahl, H. Search for Related Content PubMed PubMed Citation Articles by Fischer, R.-J. Articles by Bahl, H.

Transcription of the pst Operon of Clostridium acetobutylicum Is Dependent on Phosphate Concentration and pH

Ralf-Jörg Fischer, Sonja Oehmcke, Uta Meyer, Maren Mix, Katrin Schwarz, Tomas Fiedler, and Hubert Bahl^*

Division of Microbiology, Institute of Biological Sciences, University of Rostock, Rostock, Germany

Received 7 April 2006/ Accepted 22 May 2006

The pst operon of Clostridium acetobutylicum ATCC 824 comprises five genes, pstS, pstC, pstA, pstB, and phoU, and shows a gene architecture identical to that of Escherichia coli. Deduced proteins are predicted to represent a high-affinity phosphate-specific ABC (ATP-binding cassette) transport system (Pst) and a protein homologous to PhoU, a negative phosphate regulon regulator. We analyzed the expression patterns of the pst operon in P_i-limited chemostat cultures during acid production at pH 5.8 or solvent production at pH 4.5 and in response to P_i pulses. Specific mRNA transcripts were found only when external P_i concentrations had dropped below 0.2 mM. Two specific transcripts were detected, a 4.7-kb polycistronic mRNA spanning the whole operon and a quantitatively dominating 1.2-kb mRNA representing the first gene, pstS. The mRNA levels clearly differed depending on the external pH. The amounts of the full-length mRNA detected were about two times higher at pH 5.8 than at pH 4.5. The level of pstS mRNA increased by a factor of at least 8 at pH 5.8 compared to pH 4.5 results. Primer extension experiments revealed only one putative transcription start point 80 nucleotides upstream of pstS. Thus, additional regulatory sites are proposed in the promoter region, integrating two different extracellular signals, namely, depletion of inorganic phosphate and the pH of the environment. After phosphate pulses were applied to a phosphate-limited chemostat we observed faster phosphate consumption at pH 5.8 than at pH 4.5, although higher optical densities were recorded at pH 4.5.

Present address: Department of Medical Microbiology, Virology and Hygiene, University of Rostock, Schillingallee 70, D-18057 Rostock, Germany.

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

This article has been cited by other articles:

• Kirkland, P. A., Gil, M. A., Karadzic, I. M., Maupin-Furlow, J. A. (2008). Genetic and Proteomic Analyses of a Proteasome-Activating Nucleotidase A Mutant of the Haloarchaeon Haloferax volcanii. J. Bacteriol. 190: 193-205 [Abstract] [Full Text]