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

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.