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Journal of Bacteriology, April 2005, p. 2297-2307, Vol. 187, No. 7
0021-9193/05/$08.00+0     doi:10.1128/JB.187.7.2297-2307.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Role of the Extracytoplasmic Function Protein Family Sigma Factor RpoE in Metal Resistance of Escherichia coli{dagger}

Monique Egler,1,{ddagger} Cornelia Grosse,1,{ddagger} Gregor Grass,1 and Dietrich H. Nies1*

Institut für Mikrobiologie, Halle, Germany1

Received 28 September 2004/ Accepted 19 December 2004

RpoE of Escherichia coli is a sigma factor of the extracytoplasmic function protein family and is required for the expression of proteins involved in maintaining the integrity of periplasmic and outer membrane components. RpoE of E. coli was needed for full resistance to Zn(II), Cd(II), and Cu(II). Promoter gene fusion and quantitative real time reverse transcription (RT)-PCR (qRT-PCR) assays demonstrated that expression of RpoE was induced by metals. Global gene expression profiles upon metal treatment of a {Delta}rpoE mutant strain and its wild-type strain were analyzed with microarrays, and selected genes were confirmed by qRT-PCR. The absolute number of genes that were changed in their expression upon metal stress was similar in both strains, but the increase or decrease in transcript levels upon metal treatment was smaller in the {Delta}rpoE mutant strain than in the wild type. Genes showing increased expression in the {Delta}rpoE mutant strain encoded proteins that belong to general defense systems against protein-denaturing agents. Genes showing decreased expression were part of the RpoE modulon itself plus the ompC gene, encoding a major outer membrane protein. A {Delta}ompC deletion strain was as sensitive to Cu(II) and Cd(II) as the {Delta}rpoE mutant or a {Delta}rpoE {Delta}ompC double mutant strain. In the case of Zn(II), the double mutant was more sensitive than either single mutant. This indicates that increased expression of OmpC contributes to the RpoE modulon-mediated response to metals.

* Corresponding author. Mailing address: Institut für Mikrobiologie, Kurt-Mothes-Str. 3, 06099 Halle, Germany. Phone: (49)-345-5526352. Fax: (49)-345-5527010. E-mail: d.nies{at}mikrobiologie.uni-halle.de.

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

{ddagger} Both authors contributed equally to this study.

Journal of Bacteriology, April 2005, p. 2297-2307, Vol. 187, No. 7
0021-9193/05/$08.00+0     doi:10.1128/JB.187.7.2297-2307.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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