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Journal of Bacteriology, February 2008, p. 1027-1035, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01483-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

PhyR Is Involved in the General Stress Response of Methylobacterium extorquens AM1 ^,

Benjamin Gourion, Anne Francez-Charlot, and Julia A. Vorholt^*

Institute of Microbiology, ETH Zurich, 8093 Zurich, Switzerland

Received 13 September 2007/ Accepted 7 November 2007

PhyR represents a novel alphaproteobacterial family of response regulators having a structure consisting of two domains; a predicted amino-terminal extracytoplasmic function (ECF) sigma factor-like domain and a carboxy-terminal receiver domain. PhyR was first described in Methylobacterium extorquens AM1, in which it has been shown to be essential for plant colonization, probably due to its suggested involvement in the regulation of a number of stress proteins. Here we investigated the PhyR regulon using microarray technology. We found that the PhyR regulon is rather large and that most of the 246 targets are under positive control. Mapping of transcriptional start sites revealed candidate promoters for PhyR-mediated regulation. One of these promoters, an ECF-type promoter, was identified upstream of one-third of the target genes by in silico analysis. Among the PhyR targets are genes predicted to be involved in multiple stress responses, including katE, osmC, htrA, dnaK, gloA, dps, and uvrA. The induction of these genes is consistent with our phenotypic analyses which revealed that PhyR is involved in resistance to heat shock and desiccation, as well as oxidative, UV, ethanol, and osmotic stresses, in M. extorquens AM1. The finding that PhyR is involved in the general stress response was further substantiated by the finding that carbon starvation induces protection against heat shock and that this protection is at least in part dependent on PhyR.

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* Corresponding author. Mailing address: Institute of Microbiology, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland. Phone: 41-44-632-5524. Fax: 41-44-633-1307. E-mail: vorholt{at}micro.biol.ethz.ch

Published ahead of print on 16 November 2007.

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

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Journal of Bacteriology, February 2008, p. 1027-1035, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01483-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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