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Journal of Bacteriology, November 2008, p. 7189-7199, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00600-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

SpoT-Triggered Stringent Response Controls usp Gene Expression in Pseudomonas aeruginosa{triangledown} ,{dagger}

Nelli Boes, Kerstin Schreiber,{ddagger} and Max Schobert*

Institute of Microbiology, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany

Received 30 April 2008/ Accepted 25 August 2008

The universal stress proteins (Usps) UspK (PA3309) and UspN (PA4352) of Pseudomonas aeruginosa are essential for surviving specific anaerobic energy stress conditions such as pyruvate fermentation and anaerobic stationary phase. Expression of the respective genes is under the control of the oxygen-sensing regulator Anr. In this study we investigated the regulation of uspN and three additional P. aeruginosa usp genes: uspL (PA1789), uspM (PA4328), and uspO (PA5027). Anr induces expression of these genes in response to anaerobic conditions. Using promoter-lacZ fusions, we showed that PuspL-lacZ, PuspM-lacZ, and PuspO-lacZ were also induced in stationary phase as described for PuspN-lacZ. However, stationary phase gene expression was abolished in the P. aeruginosa triple mutant {Delta}anr {Delta}relA {Delta}spoT. The relA and spoT genes encode the regulatory components of the stringent response. We determined pppGpp and ppGpp levels using a thin-layer chromatography approach and detected the accumulation of ppGpp in the wild type and the {Delta}relA mutant in stationary phase, indicating a SpoT-derived control of ppGpp accumulation. Additional investigation of stationary phase in LB medium revealed that alkaline pH values are involved in the regulatory process of ppGpp accumulation.

* Corresponding author. Mailing address: Institute of Microbiology, Technische Universität Braunschweig, Spielmannstr. 7, D-38106 Braunschweig, Germany. Phone: 49 531 3915857. Fax: 49 531 3915854. E-mail: m.schobert{at}tu-bs.de

{triangledown} Published ahead of print on 5 September 2008.

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

{ddagger} Present address: Bioinformatics and Biochemistry, Technische Universität Braunschweig, Spielmannstr. 7, D-38106 Braunschweig, Germany.

Journal of Bacteriology, November 2008, p. 7189-7199, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00600-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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