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The Pasteurella multocida toxin is encoded within a lysogenic bacteriophage

Gillian D Pullinger1, Thomas Bevir, Alistair J Lax

  • 1Department of Microbiology, Dental Institute, King's College London, London, UK. gillian.pullinger@kcl.ac.uk

Molecular Microbiology
|December 4, 2003
PubMed

Insights

Toxigenic Pasteurella multocida harbors a prophage containing the Pasteurella multocida toxin (PMT) gene. This bacteriophage is inducible and carries the toxin gene, explaining its horizontal acquisition and role in virulence.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Toxigenic Pasteurella multocida produces a potent mitogen, Pasteurella multocida toxin (PMT).
  • The PMT structural gene (toxA) exhibits low G+C content, suggesting horizontal acquisition.
  • The genomic location and acquisition mechanism of toxA remain unclear.

Purpose of the Study:

  • To investigate the genomic environment of the toxA gene in toxigenic P. multocida.
  • To determine if the toxA gene is associated with mobile genetic elements.
  • To characterize the bacteriophages present in toxigenic P. multocida strains.

Main Methods:

  • DNA sequencing of the regions flanking the toxA gene.
  • Bioinformatic analysis to identify homologous genes.
  • Induction of prophage lytic cycle with mitomycin C.
  • Characterization of bacteriophage genomes via restriction profiling.
  • Southern blot analysis to confirm toxA gene presence in bacteriophages.

Main Results:

  • Sequencing revealed bacteriophage tail protein and antirepressor genes adjacent to toxA, indicating prophage integration.
  • A functional restriction/modification system homologue was identified near toxA.
  • Bacteriophages were detected in culture supernatants and their production increased upon mitomycin C treatment.
  • Bacteriophages from different strains showed similar restriction profiles and sizes (45-50 kb).
  • Prophages integrated into a tRNA gene in two strains; Southern blots confirmed toxA within these bacteriophages.

Conclusions:

  • The toxA gene is located within a temperate bacteriophage (prophage) in toxigenic P. multocida.
  • This prophage is inducible and carries the PMT structural gene.
  • The prophage integration and presence explain the horizontal acquisition and potential dissemination of the toxA gene.

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