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Corynebacterium diphtheriae employs specific minor pilins to target human pharyngeal epithelial cells

Anjali Mandlik1, Arlene Swierczynski, Asis Das

  • 1Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.

Molecular Microbiology
|March 23, 2007
PubMed

Insights

Minor pilins SpaB and SpaC, not the main SpaA pilus, mediate Corynebacterium diphtheriae adherence to human pharyngeal cells. These minor pilins may also anchor directly to the cell wall for tight binding.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Bacterial pili are crucial for host tissue adherence during infection.
  • Corynebacterium diphtheriae possesses three distinct pilus structures with poorly understood adherence mechanisms.

Purpose of the Study:

  • To elucidate the specific roles of different pili in Corynebacterium diphtheriae adherence to human pharyngeal epithelial cells.
  • To identify the key components responsible for tissue tropism.

Main Methods:

  • Gene deletion studies (spaA, spaB, spaC) to assess pilus assembly and adherence.
  • Antibody blocking assays to inhibit bacterial adherence.
  • Latex bead binding assays using purified pilin proteins.
  • Immunoelectron microscopy and immunofluorescence to visualize pilin localization.

Main Results:

  • The SpaA-type pilus is sufficient for adherence, but its absence (spaA deletion) did not abolish adherence.
  • Adherence was significantly reduced upon deletion of minor pilins SpaB or SpaC.
  • Antibodies against SpaB or SpaC blocked adherence, and SpaB/SpaC-coated beads specifically bound pharyngeal cells.
  • Minor pilins were observed as cell surface clusters, independent of pilus shaft assembly.

Conclusions:

  • Specific minor pilins (SpaB and SpaC) govern the tissue tropism of Corynebacterium diphtheriae for pharyngeal cells.
  • Minor pilins can mediate adherence directly, potentially through cell wall anchoring, in addition to their role in pilus structures.

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