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Infection and Immunity, October 2008, p. 4592-4599, Vol. 76, No. 10
0019-9567/08/$08.00+0     doi:10.1128/IAI.00568-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Characterization of Chromosomal Regions Conserved in Yersinia pseudotuberculosis and Lost by Yersinia pestis ^,

Flavie Pouillot, Corinne Fayolle, and Elisabeth Carniel^*

Yersinia Research Unit, Institut Pasteur, 75724 Paris Cedex 15, France

Received 9 May 2008/ Returned for modification 23 June 2008/ Accepted 19 July 2008

The transformation of the enteropathogenic bacterium Yersinia pseudotuberculosis into the plague bacillus, Yersinia pestis, has been accompanied by extensive genetic loss. This study focused on chromosomal regions conserved in Y. pseudotuberculosis and lost during its transformation into Y. pestis. An extensive PCR screening of 78 strains of the two species identified five regions (R1 to R5) and four open reading frames (ORFs; orf1 to orf4) that were conserved in Y. pseudotuberculosis and absent from Y. pestis. Their conservation in Y. pseudotuberculosis suggests a positive selective pressure and a role during the life cycle of this species. Attempts to delete two ORFs (orf3 and orf4) from the chromosome of strain IP32953 were unsuccessful, indicating that they are essential for its viability. The seven remaining loci were individually deleted from the IP32953 chromosome, and the ability of each mutant to grow in vitro and to kill mice upon intragastric infection was evaluated. Four loci (orf1, R2, R4, and R5) were not required for optimal growth or virulence of Y. pseudotuberculosis. In contrast, orf2, encoding a putative pseudouridylate synthase involved in RNA stability, was necessary for the optimal growth of IP32953 at 37°C in a chemically defined medium (M63S). Deletion of R1, a region predicted to encode the methionine salvage pathway, altered the mutant pathogenicity, suggesting that the availability of free methionine is severely restricted in vivo. R3, a region composed mostly of genes of unknown functions, was necessary for both optimal growth of Y. pseudotuberculosis at 37°C in M63S and for virulence. Therefore, despite their loss in Y. pestis, five of the nine Y. pseudotuberculosis-specific chromosomal loci studied play a role in the survival, growth, or virulence of this species.

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* Corresponding author. Mailing address: Yersinia Research Unit, Institut Pasteur, 28 Rue du Dr. Roux, 75724 Paris Cedex 15, France. Phone: (33) 1-45-68-83-26. Fax: (33) 1-40-61-30-01. E-mail: elisabeth.carniel{at}pasteur.fr

Published ahead of print on 4 August 2008.

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

Editor: J. B. Bliska

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Infection and Immunity, October 2008, p. 4592-4599, Vol. 76, No. 10
0019-9567/08/$08.00+0     doi:10.1128/IAI.00568-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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