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Three-component-mediated serotype conversion in Pseudomonas aeruginosa by bacteriophage D3

G J Newton1, C Daniels, L L Burrows

  • 1Department of Microbiology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Molecular Microbiology
|March 17, 2001
PubMed

Insights

Bacteriophage D3 alters Pseudomonas aeruginosa PAO1

Area of Science:

  • Microbiology
  • Virology
  • Molecular Biology

Background:

  • Pseudomonas aeruginosa PAO1 is a common pathogen.
  • Bacteriophages can alter bacterial surface structures.
  • Lysogenic conversion modifies bacterial serotype.

Purpose of the Study:

  • Investigate the mechanism of bacteriophage D3-mediated lysogenic conversion in Pseudomonas aeruginosa PAO1.
  • Identify the specific genes responsible for serotype conversion.

Main Methods:

  • Isolation and characterization of a DNA fragment from bacteriophage D3.
  • Transformation of Pseudomonas aeruginosa PAO1 with the D3 DNA fragment.
  • Analysis of lipopolysaccharide (LPS) structure using SDS-PAGE and antibody reactivity.
  • Identification of open reading frames (ORFs) involved in conversion.

Main Results:

  • A 3.6 kb fragment of the D3 genome mediated serotype conversion from O5 to O16.
  • Transformed bacteria showed altered LPS banding patterns and O-acetylation.
  • Three ORFs (iap, oac, wzybeta) were identified as essential for serotype conversion.
  • Iap inhibits O5 LPS assembly, allowing Wzybeta to form O16 LPS.
  • Oac O-acetylates the N-acetylfucosamine moiety of the O-antigen.

Conclusions:

  • Bacteriophage D3 utilizes a three-gene system (iap, oac, wzybeta) to convert the O-antigen serotype of Pseudomonas aeruginosa PAO1.
  • This mechanism involves inhibition of the host LPS polymerase and introduction of a phage-encoded polymerase.
  • The phage also modifies the O-antigen structure through O-acetylation.
  • This study elucidates a novel mechanism of bacteriophage-mediated bacterial surface modification.

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