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1 Yersinia Research Unit, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France
2 General Microbiology, Faculty of Biosciences, FIN-00014 University of Helsinki, Finland
Correspondence
Elisabeth Carniel
carniel2{at}pasteur.fr
Yersinia pestis is a species that emerged recently from Yersinia pseudotuberculosis and gained an exceptional pathogenicity potential. Among the major genetic differences between the plague bacillus and its ancestor is the acquisition of the pPla plasmid, which has been associated with the increased virulence of Y. pestis. In a previous study, introduction of pPla into Y. pseudotuberculosis did not lead to any modification of the virulence of the host bacterium. However, it was subsequently demonstrated that the presence of smooth lipopolysaccharide (LPS) inhibits the activity of Pla. In this study, pPla was introduced into a Y. pseudotuberculosis strain expressing smooth LPS, and into a variant in which a mutation that abrogates the formation of O-antigen (O-Ag) repeats (as in natural isolates of Y. pestis) was generated. It was found that in both strains, Pla was synthesized, exported to the bacterial membrane and processed as in Y. pestis. However, the ability of Pla to activate plasminogen was weak and observed only at 37 °C in the smooth strain, while this activity was similar to that of Y. pestis and expressed at both 28 and 37 °C in the O-Ag mutant strain. Similarly, Pla-mediated inactivation of the antiprotease 
2-antiplasmin was not detected in the smooth Y. pseudotuberculosis strain grown at 28 °C, but was expressed at both temperatures in the O-Ag mutant strain. Despite the more efficient activity of Pla, the Y. pseudotuberculosis O-Ag mutant strain exhibited a lower pathogenicity upon subcutaneous infection of mice. The results thus indicate that, although abrogation of O side chain synthesis in a Y. pseudotuberculosis strain harbouring pPla potentiates the two proteolytic activities of Pla, this is not sufficient to confer to Y. pseudotuberculosis a higher pathogenicity potential. These results also suggest that acquisition of pPla may not have been sufficient to confer an immediate higher pathogenic potential to the ancestor Y. pestis strain.
2AP, 2-antiplasmin; ECM, extracellular matrix; LPS, lipopolysaccharide; O-Ag, O-antigen; sc, subcutaneous; Tmp, trimethoprimThis article has been cited by other articles:
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  T. Blisnick, P. Ave, M. Huerre, E. Carniel, and C. E. Demeure Oral Vaccination against Bubonic Plague Using a Live Avirulent Yersinia pseudotuberculosis Strain Infect. Immun., August 1, 2008; 76(8): 3808 - 3816. [Abstract] [Full Text] [PDF]
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E. M. Galvan, M. A. S. Lasaro, and D. M. Schifferli Capsular Antigen Fraction 1 and Pla Modulate the Susceptibility of Yersinia pestis to Pulmonary Antimicrobial Peptides Such as Cathelicidin Infect. Immun., April 1, 2008; 76(4): 1456 - 1464. [Abstract] [Full Text] [PDF]
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 T.-J. Kim, S. Chauhan, V. L. Motin, E.-B. Goh, M. M. Igo, and G. M. Young Direct Transcriptional Control of the Plasminogen Activator Gene of Yersinia pestis by the Cyclic AMP Receptor Protein J. Bacteriol., December 15, 2007; 189(24): 8890 - 8900. [Abstract] [Full Text] [PDF]
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 F. Pouillot, C. Fayolle, and E. Carniel A putative DNA adenine methyltransferase is involved in Yersinia pseudotuberculosis pathogenicity Microbiology, August 1, 2007; 153(8): 2426 - 2434. [Abstract] [Full Text] [PDF]
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