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Infection and Immunity, August 2004, p. 4424-4431, Vol. 72, No. 8
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.8.4424-4431.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Effects of the Enterococcus faecalis hypR Gene Encoding a New Transcriptional Regulator on Oxidative Stress Response and Intracellular Survival within Macrophages

Laboratoire de Microbiologie de l'Environnement, EA 956, USC INRA, IRBA, Université de Caen, 14032 Caen Cedex, France,¹ Institute of Microbiology, Catholic University of Sacred Heart, 00168 Rome, Italy²

Received 16 January 2004/ Returned for modification 11 March 2004/ Accepted 7 April 2004

In order to identify regulators of the oxidative stress response in Enterococcus faecalis, an important human pathogen, several genes annotated as coding for transcriptional regulators were inactivated by insertional mutagenesis. One mutant, affected in the ef2958 locus (designated hypR [hydrogen peroxide regulator]), appeared to be highly sensitive to oxidative challenge caused by hydrogen peroxide. Moreover, testing of the hypR mutant by using an in vivo-in vitro macrophage infection model resulted in a highly significant reduction in survival compared to the survival of parent strain JH2-2. Northern blot analyses were carried out with probes specific for genes encoding known antioxidant enzymes, and they showed that the ahpCF (alkyl hydroperoxide reductase) transcript was expressed less in mutant cells. Mobility shift protein-DNA binding assays revealed that HypR regulated directly the expression of hypR itself and the ahpCF operon. Our combined results showed that HypR appeared to be directly involved in the expression of ahpCF genes under oxidative stress conditions and suggested that this regulator could contribute to the virulence of E. faecalis.

Editor: F. C. Fang

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