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Biological roles of nontypeable Haemophilus influenzae type IV pilus proteins encoded by the pil and com operons

Michael D Carruthers1, Erin N Tracy, Amanda C Dickson

  • 1Center for Microbial Pathogenesis, The Research Institute at Nationwide Children’s Hospital and Department of Pediatrics, College of Medicine, The Ohio State University, Columbus, Ohio, USA.

Journal of Bacteriology
|February 14, 2012
PubMed

Insights

All genes in the pil and com clusters are essential for nontypeable Haemophilus influenzae (NTHI) type IV pilus (Tfp) function, impacting adherence, biofilm formation, and natural transformation. PilA is identified as the major Tfp subunit.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Nontypeable Haemophilus influenzae (NTHI) is an opportunistic human respiratory pathogen.
  • Previous studies indicated the necessity of pil and com gene products for type IV pilus (Tfp) biogenesis and function in NTHI.

Purpose of the Study:

  • To elucidate the operon structure of the pilABCD and comABCDEF gene clusters in NTHI.
  • To determine the essentiality of each gene product within these clusters for Tfp function.
  • To identify the major pilin subunit of NTHI Tfp.

Main Methods:

  • Construction and analysis of nonpolar deletion mutants for each of the 10 pil and com genes.
  • Assessment of bacterial adherence to primary human airway cells.
  • In vitro biofilm formation assays.
  • Natural transformation efficiency assays.
  • Immunogold labeling and mass spectrometry to identify the major pilin subunit.

Main Results:

  • The pilABCD and comABCDEF gene clusters were confirmed as operons, with each gene product being essential for normal pilus function.
  • Mutants lacking any of these genes exhibited defects in adherence to human airway cells, biofilm formation, and natural transformation.
  • PilA was identified as the major type IV pilin protein expressed by NTHI.

Conclusions:

  • Each gene within the pil and com operons is crucial for the biogenesis and/or function of NTHI Tfp.
  • The identification of PilA as the major pilin subunit provides a target for further research.
  • Understanding these pilus components offers potential for developing Tfp-derived vaccines or pilus-directed therapeutics against NTHI-induced diseases.

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