Hostile takeover factors of Pseudomonas
File(s)
Author(s)
Collins, Alice
Type
Thesis
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic pulmonary infections in Cystic Fibrosis patients, dominating and damaging the lung environment. P. aeruginosa can deliver bacterial-derived toxins into competing neighbours to inhibit growth or kill via the contact-dependent inhibition (CDI) and Type VI Secretion Systems (T6SS). However, the role of CDI systems in Pseudomonas infection in Cystic Fibrosis clinical isolates remains unclear. Here we bioinformatically and experimentally investigate the CDI and T6SSs encoded in P. aeruginosa strain PA14. For CDI systems, bioinformatics was used to elucidate and evaluate genetic domains to determine putative toxin-immunity module functions. I show that PA14 encodes two CDI systems with putative tRNase activities and demonstrate that both CDI systems encode a functional toxin/immunity pair, further supporting their role in antibacterial activity. I identified regions conserved between and within genetically distinct system types to produce recombinant proteins for antibody production for use as a tool to determine CDI activation status in clinical isolates. We constructed whole operon deletion mutants and see no impact of these systems upon motility or biofilm formation. However, we show a role for both CDI systems in interbacterial competition with potential interplay between the CDI and T6SSs. Finally, we show an unprecedented level of control for the H2-T6SSs by enhancer binding protein Sfa2 in addition to a previously unseen role of RpoN in CDI system expression. This study further delineates the genomic organisation and role of CDI systems in P. aeruginosa interbacterial competition which may contribute to the niche dominance observed in P. aeruginosa infection. We propose the use of competitive systems as a mechanism of P. aeruginosa dominance in the CF lung.
Version
Open Access
Date Issued
2023-07-04
Date Awarded
01/09/2023
License URL
Advisor
Allsopp, Luke
Davies, Jane
Publisher Department
NHLI
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)