| Summary: | Pseudomonas aeruginosa is a widespread opportunistic pathogen in many chronic
biofilm-based infections. The Pf4 filamentous bacteriophage in PAO1 was previously
shown to play an important role during biofilm formation. In particular, the
superinfective morphotype was found to be critical for cell death, biofilm dispersal,
and variant formation. A putative repressor c homolog, located within the intergenic
region between PA0716 and PA0717 in the Pf4 phage genome, is suspected to play
a role in protection of the lysogenised bacterial host from Pf4 reinfection. Mutations
in this repressor c gene have also been observed in superinfective Pf4. In this study,
a plasmid encoding repressor c was constructed to perform in vitro immunity assays
to test its role in immunity. Binding assays were also carried out to determine
repressor C binding to its upstream putative promoter region. It was observed that
repressor C was able to bind to the putative promoter and prevent plaque formation
in the immunity assay. Furthermore, the protein failed to bind to a promoter carrying
two single nucleotide polymorphisms found in the superinfective phage. The findings
of this study provide evidence that the putative repressor c and its promoter region
confer immunity to PAO1 against reinfections by Pf4 phage.
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