Modulation of Pertussis and Adenylate Cyclase Toxins by Sigma Factor RpoE in Bordetella pertussis

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Mariette Barbier1, Dylan T Boehm1, Emel Sen-Kilic1

  • 1Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA.

Infection and Immunity
|November 17, 2016
PubMed

Insights

Bordetella pertussis RpoE, a stress-response sigma factor, unexpectedly reduces pertussis toxin (PT) production while increasing adenylate cyclase toxin (ACT) secretion. This RpoE activity impacts B. pertussis virulence and host cell interactions.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Bordetella pertussis causes whooping cough, utilizing toxins like pertussis toxin (PT) and adenylate cyclase toxin (ACT) for infection.
  • Sigma factors, such as RpoE, regulate bacterial stress responses, while their negative regulators, like RseA, control their activity.
  • The function of many B. pertussis transcription factors, including RpoE, remains largely uncharacterized.

Purpose of the Study:

  • To investigate the role of the RpoE sigma factor in B. pertussis virulence.
  • To identify the genes regulated by RpoE in B. pertussis.
  • To understand the relationship between RpoE activity and the expression of key virulence factors PT and ACT.

Main Methods:

  • Comparative analysis of wild-type B. pertussis and an rseA deletion mutant (PM18) with elevated RpoE activity.
  • Murine airway infection models to assess bacterial virulence.
  • Phagocyte killing assays.
  • RNA sequencing (RNA-seq) to determine RpoE-regulated genes.
  • Western blotting and proteomic analysis to quantify toxin levels.

Main Results:

  • The rseA deletion mutant (PM18), exhibiting high RpoE activity, showed reduced virulence in murine airways and increased susceptibility to phagocytes.
  • RNA-seq identified 263 genes differentially regulated by RpoE.
  • Surprisingly, the high-RpoE-activity mutant produced significantly less pertussis toxin (PT) compared to the wild-type strain.
  • ACT secretion was high in the mutant, but PT levels were inversely correlated with RpoE activity.

Conclusions:

  • Elevated RpoE activity in B. pertussis negatively impacts PT production, despite increasing ACT secretion.
  • RpoE influences B. pertussis virulence and survival within host cells, potentially through complex regulatory networks.
  • The study reveals an inverse relationship between PT and ACT expression modulated by RpoE, suggesting intricate control over virulence factor production.
Keywords:
Bordetella pertussisRpoEadenylate cyclase toxinpertussis toxin

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