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Journal of Bacteriology, November 2007, p. 8034-8043, Vol. 189, No. 22
0021-9193/07/$08.00+0     doi:10.1128/JB.00900-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Biofilm Formation-Gene Expression Relay System in Escherichia coli: Modulation of ^S-Dependent Gene Expression by the CsgD Regulatory Protein via ^S Protein Stabilization ^,

Luciana Gualdi, Letizia Tagliabue, and Paolo Landini^*

Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy

Received 8 June 2007/ Accepted 4 September 2007

Bacteria can switch from a single-cell (planktonic) mode to a multicellular community (biofilm) mode via production of cell-cell aggregation and surface adhesion factors. In this report, we present evidence that the CsgD protein, a transcription regulator involved in biofilm formation in Escherichia coli, modulates the expression of the rpoS (^S) regulon. Protein pattern analysis of E. coli cells in stationary phase shows that CsgD affects the expression of several proteins encoded by ^S-dependent genes. CsgD regulation of ^S-dependent genes takes place at gene transcription level, does not bypass the need for rpoS, and is abolished in an rpoS-null mutant. Consistent with these results, we find that CsgD expression leads to an increase in ^S intracellular concentration. Increase in ^S cellular amount is mediated by CsgD-dependent transcription activation of iraP, encoding a factor involved in ^S protein stabilization. Our results strongly suggest that the CsgD regulatory protein plays a major role as a relay between adhesion factors production and ^S-dependent gene expression via ^S protein stabilization. Direct coordination between biofilm formation and expression of the rpoS regulon could positively impact important biological processes, such as host colonization or response to environmental stresses.

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* Corresponding author. Mailing address: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy. Phone: 39-02-50315028. Fax: 39-02-50315044. E-mail: paolo.landini{at}unimi.it

Published ahead of print on 14 September 2007.

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

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Journal of Bacteriology, November 2007, p. 8034-8043, Vol. 189, No. 22
0021-9193/07/$08.00+0     doi:10.1128/JB.00900-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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