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Journal of Bacteriology, June 2009, p. 3717-3725, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01741-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Growth Phase and Metal-Dependent Transcriptional Regulation of the fecA Genes in Helicobacter pylori{triangledown}

Alberto Danielli,1,{dagger} Simona Romagnoli,1,{dagger} Davide Roncarati,1 Lorenzo Costantino,1,{ddagger} Isabel Delany,2 and Vincenzo Scarlato1,2*

Department of Biology, University of Bologna, Bologna, Italy,1 Molecular Microbiology Unit, Novartis Vaccines and Diagnostics, Siena, Italy2

Received 12 December 2008/ Accepted 28 March 2009

Balancing metal uptake is essential for maintaining a proper intracellular metal concentration. Here, we report the transcriptional control exerted by the two metal-responsive regulators of Helicobacter pylori, Fur (iron-dependent ferric uptake regulator) and NikR (nickel-responsive regulator), on the three copies of the fecA genes present in this species. By monitoring the patterns of transcription throughout growth and in response to nickel, iron, and a metal chelator, we found that the expression of the three fecA genes is temporally regulated, responds to metals in different ways, and is selectively controlled by either one of the two regulators. fecA1 is expressed at a constant level throughout growth, and its expression is iron sensitive; the expression of fecA2 is mainly off, with minor expression coming up in late exponential phase. In contrast, the expression of fecA3 is maximal in early exponential phase, gradually decreases with time, and is repressed by nickel. The direct roles of Fur and NikR were studied both in vitro, by mapping the binding sites of each regulator on the promoter regions via DNase I footprinting analysis, and in vivo, by using primer extension analyses of the fecA transcripts in fur and nikR deletion strains. Overall, the results show that the expression of each fecA gene is finely tuned in response to metal availability, as well as during the bacterial growth phase, suggesting specific and dedicated functions for the three distinct FecA homologues.

* Corresponding author. Mailing address: Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy. Phone: 39 051 209 4204. Fax: 39 051 209 4286. E-mail: vincenzo.scarlato{at}unibo.it

{triangledown} Published ahead of print on 3 April 2009.

{dagger} These authors contributed equally.

{ddagger} Present address: Department of Molecular Biology, University of Geneva, Sciences III, 30, quai Ernest-Ansermet, CH-1211, Geneva 4, Switzerland.

Journal of Bacteriology, June 2009, p. 3717-3725, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01741-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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