AUTHOR=Hu Jia , Zhu Mei-Jun 

TITLE=Defects in polynucleotide phosphorylase impairs virulence in Escherichia coli O157:H7

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00806

DOI=10.3389/fmicb.2015.00806

ISSN=1664-302X

ABSTRACT=<p>Polynucleotide phosphorylase (PNPase) is reported to regulate virulence in <italic>Salmonella, Yersinia</italic> sp. and <italic>Campylobacter jejuni</italic>, yet its role in <italic>Escherichia coli</italic> O157:H7 has not been investigated. To gain insights into its roles in <italic>E. coli</italic> O157:H7 virulence, <italic>pnp</italic> deletion mutants were generated and the major virulence factors were compared to their parental wild type strains. Deletion of <italic>pnp</italic> in <italic>E. coli</italic> O157:H7 dramatically decreased <italic>stx2</italic> mRNA expression and Stx2 protein production, and impaired lambdoid prophage activation in <italic>E. coli</italic> O157:H7. Quantitative PCR further confirmed that the Stx2 phage lytic growth was repressed by <italic>pnp</italic> 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 <italic>pnp</italic> in <italic>E. coli</italic> O157:H7 decreased its adhesion to intestinal epithelial cells as well as cattle colonic explant tissues. On the other hand, PNPase inactivation in <italic>E. coli</italic> 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 <italic>E. coli</italic> O157:H7.</p>