Campylobacter is a bacterial pathogen commonly responsible for foodborne gastroenteritis worldwide. Due to the rapid development of resistance to antibiotics, many alternative interventions have been studied and bacteriophage therapy is one of them. To maximise the impact of the intervention and to ensure it remains sustainable it important to study the ecology and coevolution of Campylobacter and the bacteriophage that infect the pathogen. Coevolution interactions between Campylobacter and bacteriophage drive rapid molecular change and contribute to a higher mutation rates for both parties. In this study genetic modifications were examined in the bacterial host and phage arising either in vivo or in vitro. We observed the impact of C. jejuni containing Mu-like pro-phage on campylobacters populating the caeca of commercial broiler flocks. The Mu-containing campylobacters initially colonised and became the dominant strain, only to be out-competed before depopulation of the broiler house. The presence of the transposable Mu-like prophage ultimately proved to be a limitation in the fitness of the host. Campylobacter-specific phage CP30 is a T4-like phage of the Eucampyvirinae that was isolated from a farm with several other phage showing differences in host range of contemporary farm isolates. After serial passage the phage population acquired sequence variants. One newly characterised sequence type, CP30C, was defective in a tail fibre protein and revealed reduced adsorption ability and sensitivity against C. jejuni host strains. Whole genome sequencing identified host mutation in C. jejuni carrier state strains that maintain viability despite the continual production of virulent phage. A point mutation in the flhF gene (flhF(T368A)) was hypothesised to contribute to the non-motile phenotype of carrier state strains. Expression of flhF(T368A) in a flhF knockout background provedto have impaired motility, exhibit structural defects in flagella synthesis, were less susceptible to phage infection and show down regulation of σ28 dependent and σ54 dependent flagellar associated genes. Recombinant protein expression of FlhF demonstrated the protein to have GTPase activity and the FlhF(T368A) to have reduced enzyme activity, greater thermal sensitivity and to be impaired in protein folding compared to wild type FlhF.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:722479 |
| Date | January 2017 |
| Creators | Liang, Lu |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/41924/ |
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