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Front Microbiol. 2015 Aug 17;6:806. doi: 10.3389/fmicb.2015.00806. eCollection 2015.

Defects in polynucleotide phosphorylase impairs virulence in Escherichia coli O157:H7.

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School of Food Science, Washington State University, Pullman, WA USA ; Department of Animal Science, University of Wyoming, Laramie, WY USA.
School of Food Science, Washington State University, Pullman, WA USA.


Polynucleotide phosphorylase (PNPase) is reported to regulate virulence in Salmonella, Yersinia sp. and Campylobacter jejuni, yet its role in Escherichia coli O157:H7 has not been investigated. To gain insights into its roles in E. coli O157:H7 virulence, pnp deletion mutants were generated and the major virulence factors were compared to their parental wild type strains. Deletion of pnp in E. coli O157:H7 dramatically decreased stx2 mRNA expression and Stx2 protein production, and impaired lambdoid prophage activation in E. coli O157:H7. Quantitative PCR further confirmed that the Stx2 phage lytic growth was repressed by pnp deletion. Consistent with reduced Stx2 production and Stx2 phage activation, the transcriptional levels of genes involved in phage lysis and replication were down-regulated. In addition, disruption of pnp in E. coli O157:H7 decreased its adhesion to intestinal epithelial cells as well as cattle colonic explant tissues. On the other hand, PNPase inactivation in E. coli O157:H7 enhanced Tir protein content and the transcription of type three secretion system components, including genes encoding intimin, Tir, and EspB as well as locus of enterocyte and effacement positive regulator, Ler. Collectively, data indicate that PNPase has pleiotropic effects on the virulence of E. coli O157:H7.


E. coli O157:H7; PNPase; Shiga toxin 2; Type three secretion system; adhesion; epithelium; intestine; prophage

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