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Cyclic di-GMP riboswitch-regulated type IV pili contribute to aggregation of Clostridium difficile

Eric Bordeleau1, Erin B Purcell2, Daniel A Lafontaine1

  • 1Département de Biologie, Faculté des Sciences, Université de Sherbrooke, QC, Canada.

Journal of Bacteriology
|December 17, 2014
PubMed

Insights

Cyclic diguanosine monophosphate (c-di-GMP) promotes Clostridium difficile cell aggregation by upregulating type IV pilus (T4P) gene transcription via a riboswitch mechanism, enhancing bacterial colonization.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Clostridium difficile is an anaerobic Gram-positive bacterium causing intestinal infections.
  • Cyclic diguanosine monophosphate (c-di-GMP) is a bacterial second messenger regulating motility and aggregation.
  • Elevated c-di-GMP in C. difficile reduces motility and increases cell aggregation.

Purpose of the Study:

  • Investigate the role of the type IV pilus (T4P) locus in c-di-GMP-dependent cell aggregation.
  • Elucidate the regulatory mechanism of T4P gene expression by c-di-GMP.

Main Methods:

  • Gene inactivation of pilA1 and pilB1 to assess pilus formation and aggregation.
  • Analysis of T4P gene transcript levels under varying c-di-GMP concentrations.
  • In vitro transcription assays to confirm riboswitch activity.

Main Results:

  • Inactivation of pilA1 and pilB1 genes abolished pilus formation and reduced cell aggregation.
  • High intracellular c-di-GMP levels increased T4P gene transcript levels.
  • In vitro assays confirmed c-di-GMP-dependent activation of transcription via a riboswitch.

Conclusions:

  • Type IV pili are crucial for c-di-GMP-mediated cell aggregation in C. difficile.
  • A c-di-GMP-responsive riboswitch upregulates T4P gene transcription.
  • This regulatory pathway promotes bacterial cell aggregation in C. difficile.

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