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Infection and Immunity, January 2005, p. 563-572, Vol. 73, No. 1
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.1.563-572.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Comparative Analysis of the Roles of HtrA-Like Surface Proteases in Two Virulent Staphylococcus aureus Strains

Candice Rigoulay,1* José M. Entenza,2 David Halpern,1 Eleonora Widmer,2 Philippe Moreillon,2 Isabelle Poquet,1 and Alexandra Gruss1

Unité de Recherches Laitières et Génétique Appliquée, Institut National de la Recherche Agronomique, Jouy en Josas, France,1 Institute of Fundamental Microbiology, Dorigny, Lausanne, Switzerland2

Received 29 June 2004/ Returned for modification 30 August 2004/ Accepted 22 September 2004

The HtrA surface protease is involved in the virulence of many pathogens, mainly by its role in stress resistance and bacterial survival. Staphylococcus aureus encodes two putative HtrA-like proteases, referred to as HtrA1 and HtrA2. To investigate the roles of HtrA proteins in S. aureus, we constructed htrA1, htrA2, and htrA1 htrA2 insertion mutants in two genetically different virulent strains, RN6390 and COL. In the RN6390 context, htrA1 inactivation resulted in sensitivity to puromycin-induced stress. The RN6390 htrA1 htrA2 mutant was affected in the expression of several secreted virulence factors comprising the agr regulon. This observation was correlated with the disappearance of the agr RNA III transcript in the RN6390 htrA1 htrA2 mutant. The virulence of this mutant was diminished in a rat model of endocarditis. In the COL context, both HtrA1 and HtrA2 were essential for thermal stress survival. However, only HtrA1 had a slight effect on exoprotein expression. The htrA mutations did not diminish the virulence of the COL strain in the rat model of endocarditis. Our results indicate that HtrA proteins have different roles in S. aureus according to the strain, probably depending on specific differences in the regulation of virulence factor and stress protein expression. We propose that HtrA1 and HtrA2 contribute to pathogenicity by controlling the production of certain extracellular factors that are crucial for bacterial dissemination, as revealed in the RN6390 background. We speculate that HtrA proteins act in the agr-dependent regulation pathway by assuring folding and/or maturation of some surface components of the agr system.

* Corresponding author. Mailing address: Unité de Recherches Laitières et Génétique Appliquée, INRA, 78352 Jouy-en-Josas Cedex, France. Phone: 33-1-34 65 20 91. Fax: 33-1-34 65 20 65. E-mail: rigoulay{at}jouy.inra.fr.

Editor: V. J. DiRita

Infection and Immunity, January 2005, p. 563-572, Vol. 73, No. 1
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.1.563-572.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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