ppGpp with DksA controls gene expression in the locus of enterocyte effacement (LEE) pathogenicity island of enterohaemorrhagic Escherichia coli through activation of two virulence regulatory genes

Authors

  • Noriko Nakanishi,

    1. Division of Applied Microbiology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
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  • Hiroyuki Abe,

    1. Division of Applied Microbiology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
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  • Yoshitoshi Ogura,

    1. Division of Microbiology, Department of Infectious Diseases and
    2. Division of Bioenvironmental Science, Frontier Science Research Center, Faculty of Medicine, University of Miyazaki, Miyazaki, 5200 Kiyotake, Miyazaki 899-1692, Japan.
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  • Tetsuya Hayashi,

    1. Division of Microbiology, Department of Infectious Diseases and
    2. Division of Bioenvironmental Science, Frontier Science Research Center, Faculty of Medicine, University of Miyazaki, Miyazaki, 5200 Kiyotake, Miyazaki 899-1692, Japan.
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  • Kosuke Tashiro,

    1. Department of Genetic Resources Technology, Faculty of Agriculture, Kyusyu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
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  • Satoru Kuhara,

    1. Department of Genetic Resources Technology, Faculty of Agriculture, Kyusyu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
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  • Nakaba Sugimoto,

    1. Division of Applied Microbiology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
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  • Toru Tobe

    Corresponding author
    1. Division of Applied Microbiology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
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Summary

For a new pathogen to emerge, it must acquire both virulence genes and a system for responding to changes in environmental conditions. Starvation of nutrients or growth arrest induces the stringent response in Escherichia coli, via increased ppGpp. We found the adherence capacity of enterohaemorrhagic E. coli (EHEC) and gene expression in the locus of enterocyte effacement (LEE) were enhanced by a downshift in nutrients or by entry into the stationary growth phase, both of which increase the ppGpp concentration. The activation was dependent on relA and spoT, which encode enzymes for the synthesis and degradation of ppGpp, and on dksA, which encodes an RNA polymerase accessory protein required for the stringent response. Upon induction of RelA expression, LEE gene transcription was activated within 20 min, even without starvation. The expression of two LEE transcriptional regulators, Ler and Pch, was activated by ppGpp and essential for the enhancement of LEE gene expression. In addition, the ler and pch promoters were directly activated by ppGpp in an in vitro transcription system. These findings suggest that the regulation of virulence genes in EHEC is integrated with E. coli's stringent response system, through the regulation of virulence regulatory genes.

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