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Updated: Oct 19, 2026

High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability
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High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability

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Functional characterization of type IV pili expressed on diarrhea-associated isolates of Aeromonas species

S M Kirov1, L A O'Donovan, K Sanderson

  • 1Discipline of Pathology, University of Tasmania, Hobart, Tasmania 7001, Australia. S.M.Kirov@utas.edu.au

Infection and Immunity
|September 25, 1999
PubMed

Insights

Bundle-forming pili (Bfp) from Aeromonas bacteria are key intestinal colonization factors. These pili mediate bacterial adhesion to human enterocytes, crucial for infection.

Area of Science:

  • Microbiology
  • Cell Biology
  • Infectious Diseases

Background:

  • Diarrhea-associated Aeromonas species predominantly express long, flexible type IV pili, termed bundle-forming pili (Bfp).
  • Previous reports suggest Bfp function as intestinal colonization factors.

Purpose of the Study:

  • To provide compelling evidence that Bfp are intestinal colonization factors.
  • To elucidate the role of Bfp in Aeromonas adhesion to host intestinal cells.

Main Methods:

  • Adhesion assays using Aeromonas bacteria and purified Bfp with various cell lines and intestinal tissues.
  • Light and electron microscopy, immunohistochemical detection.
  • Mechanical removal of Bfp, dose-dependent inhibition assays with purified Bfp and anti-Bfp antibodies (Fab fraction).
  • Ultrastructural studies including ruthenium red staining and transmission/scanning electron microscopy.

Main Results:

  • Aeromonas bacteria and purified Bfp demonstrated significant adherence to epithelial and intestinal cell lines, human enterocytes, and human/rabbit intestinal tissues.
  • Mechanical removal of Bfp reduced bacterial adhesion by up to 80%.
  • Purified Bfp and anti-Bfp antibodies dose-dependently inhibited bacterial adhesion.
  • Ultrastructural studies confirmed pilus-mediated adhesion and suggested Bfp's role in bacterium-to-bacterium linkages.
  • Bfp-positive isolates did not exhibit type IV pilus-mediated twitching motility.

Conclusions:

  • Bundle-forming pili (Bfp) are critical for the intestinal colonization of diarrhea-associated Aeromonas species.
  • Bfp mediate bacterial adhesion to human enterocytes, representing a primary mechanism for colonization.
  • Bfp may also contribute to colonization through bacterium-to-bacterium interactions.

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