The effect of active prophage carriage on the virulence of Pseudomonas aeruginosa

The Liverpool epidemic strain (LES) of Pseudomonas aeruginosa is a key opportunistic pathogen and major cause of death in cystic fibrosis (CF) patients. The bacterium establishes biofilm communities, contributing to immune evasion and adaptation to the CF lung. The success of LES is associated with a set of bacterial viruses called bacteriophages (phages). There are five temperate phages integrated into the LES genome as active prophages, which provide fitness advantages, but can also be induced to their replicative form and destroy their host by lysis. Active phages are very common in the CF lung and infecting P. aeruginosa strains commonly carry many prophages, but little is known about the co-operative interactions between the two. This project investigates the relationship between three active LES phages (LES phage 2, 3 and 4) and the model bacterial host strain PAO1.In vitro culture experiments revealed that the LES prophages affect the growth rate of PAO1 differently depending on the availability of nutrients. Whilst little difference was observed under nutrient rich conditions, prophage carriage significantly hindered growth when nutrients were limited, reaching a maximum optical density 85.8% of that reached by the Wildtype (WT). Biofilm density assays indicated that LES phage carriage significantly enhanced biofilm formation by between 44% and 981% when nutrients were readily available (P <0.05). However, during nutrient starvation, most LES prophages hindered biofilm formation (P <0.05), except for prophage 2 that appeared to promote significantly thicker biofilm growth (P 0.0002). Infection experiments using the Galleria mellonella model showed that prophage carriage affected virulence and survival in vivo. The WT strain killed larvae significantly faster than strains carrying prophage (P <0.0001) despite reaching a significantly lower bacterial load than the LES phages 3 and 4 lysogens (P <0.05). These data suggest that LES prophages contribute to adaptation for longer survival in vivo.

Level dc:type.qualificationlevel

Master's Level (Level 7)

Year dc:date.issued

2022

Author dc:creator

• Plahe, G

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1320026

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1320026