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Journal of Bacteriology, May 2008, p. 3213-3224, Vol. 190, No. 9
0021-9193/08/$08.00+0     doi:10.1128/JB.01936-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Phenolic Acid-Mediated Regulation of the padC Gene, Encoding the Phenolic Acid Decarboxylase of Bacillus subtilis ^,

Ngoc Phuong Tran, Jerôme Gury, Véronique Dartois, Thi Kim Chi Nguyen, Hélène Seraut, Lise Barthelmebs,^¶ Patrick Gervais, and Jean-François Cavin^*

Laboratoire GPMA, IFR92, ENSBANA Université de Bourgogne, 1 esplanade Erasme, F-21000 Dijon, France

Received 13 December 2007/ Accepted 26 February 2008

In Bacillus subtilis, several phenolic acids specifically induce expression of padC, encoding a phenolic acid decarboxylase that converts these antimicrobial compounds into vinyl derivatives. padC forms an operon with a putative coding sequence of unknown function, yveFG, and this coding sequence does not appear to be involved in the phenolic acid stress response (PASR). To identify putative regulators involved in the PASR, random transposon mutagenesis, combined with two different screens, was performed. PadR, a negative transcriptional regulator of padC expression, was identified. padR is not located in the vicinity of padC, and the expression of padR is low and appears constitutive. This is in contrast with what occurs in other gram-positive bacteria, in which padR is autoregulated and induced by phenolic acids. Further screening of the transposon library failed to identify genes other than padR involved in the PASR. Modest inactivation of padR by phenolic acids was obtained in recombinant Escherichia coli expressing padC and padR, and this translates into induction of decarboxylase activity. Gel shift promoter binding assays performed with and without MgCl₂, and with and without phenolic acids, demonstrated that phenolic acids were able to abolish the binding of PadR to the yveFG-padC promoter in the absence of MgCl₂. Altogether, our results indicate that (i) PadR is inactivated directly by phenolic acids in vitro, (ii) inhibition of PadR in response to phenolic acids may occur without the need for a sensor-like effector in B. subtilis, and (iii) phenolic acids are able to modulate PadR activity in E. coli in the absence of any additional effector.

Published ahead of print on 7 March 2008.

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

Present address: UMR CNRS 5553, Université de Grenoble Joseph Fourier, 38400 Saint-Martin d'Héres, France.

Present address: Novartis Institute for Tropical Diseases, 10 Biopolis Rd., Singapore 138670, Singapore.

^¶ Present address: Laboratoire BIOMEM, Université de Perpignan, 66860 Perpignan Cedex, France.