The response regulator PhoP is important for survival under conditions of macrophage-induced stress and virulence in Yersinia pestis - PubMed (original) (raw)

The response regulator PhoP is important for survival under conditions of macrophage-induced stress and virulence in Yersinia pestis

P C Oyston et al. Infect Immun. 2000 Jun.

Abstract

The two-component regulatory system PhoPQ has been identified in many bacterial species. However, the role of PhoPQ in regulating virulence gene expression in pathogenic bacteria has been characterized only in Salmonella species. We have identified, cloned, and sequenced PhoP orthologues from Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica. To investigate the role of PhoP in the pathogenicity of Y. pestis, an isogenic phoP mutant was constructed by using a reverse-genetics PCR-based strategy. The protein profiles of the wild-type and phoP mutant strains, grown at either 28 or 37 degrees C, revealed more than 20 differences, indicating that PhoP has pleiotrophic effects on gene expression in Y. pestis. The mutant showed a reduced ability to survive in J774 macrophage cell cultures and under conditions of low pH and oxidative stress in vitro. The mean lethal dose of the phoP mutant in mice was increased 75-fold in comparison with that of the wild-type strain, indicating that the PhoPQ system plays a key role in regulating the virulence of Y. pestis.

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Figures

FIG. 1

FIG. 1

Comparison of the deduced PhoP amino acid sequences of Y. pestis, Y. pseudotuberculosis (Y. ptb), Y. enterocolitica (Y. ent), E. coli, and Salmonella serovar Typhimurium (S. typhm), aligned by using Clustal V multiple sequence alignment software. Identical amino acids (●), conserved changes (|), and the essential aspartic acid residue (∗) are shown.

FIG. 2

FIG. 2

Survival of Y. pestis wild-type (GB) and phoP mutant (SAI2.2) strains after uptake by J774 macrophages. Results shown are the means of duplicate determinations in two separate experiments, with standard errors.

FIG. 3

FIG. 3

2D gel electrophoresis protein expression profiles for the Y. pestis wild-type strain (a) and Y. pestis phoP mutant strain (b) grown at 28°C. Differences in protein expression are highlighted (0). Mr, molecular weights in thousands.

FIG. 4

FIG. 4

2D gel electrophoresis protein expression profiles for the Y. pestis wild-type strain (A) and Y. pestis phoP mutant (B) grown at 37°C. Differences in protein expression are highlighted (0). Mr, molecular weight in thousands.

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