Understanding and exploiting bacteriophage-host interactions for the control and detection of listeria monocytogenes

Abstract

The hypothesis of this thesis is that phages isolated from the environment can play a role in the future to reduce outbreaks of the disease listeriosis by applying phages as biocontrol agents against the pathogen L. monocytogenes and by incorporating phages into systems for the detection of this pathogen. Phage vB_LmoH_P61, a lytic phage isolated from grass silage, was applied to food matrices for the biocontrol of L. monocytogenes which resulted in the inhibition of L. monocytogenes in artificially inoculated pasteurized milk and baby spinach. The key findings from this study show the importance of the food matrix, multiplicity of infection, the growth stage of the host bacterial cells and storage temperature for the successful application of phages as biocontrol agents. Chapter 3 of this thesis also aimed to exploit phages (phage lysins) as biocontrol agents. The key findings showed that polyhydroxyalkanoate bionanoparticles displaying the full-length endolysin of phage vB_LmoS_293 or the amidase domain of this lysin, lysed and inhibited the growth of L. monocytogenes strain 473 at 37 ºC and 22 ºC. Phages were also exploited for the capture and potential detection of L. monocytogenes (Chapter 4). A recombinant receptor binding protein from phage vB_LmoS_293 was produced and shown to capture its host-bacterial cells. Three phages—vB_LmoS_C996, vB_LmoS_P11 and vB_LmoS_P7—were isolated from grass silage and characterized. The endolysins and putative receptor binding proteins were identified in the genomes of these phages, and these proteins may be exploited in future applications for the biocontrol and detection of L. monocytogenes. In this thesis, new phages have been isolated, new protocols developed for the inhibition of L. monocytogenes, a potential new delivery system of phage lysins has been shown and new protocols developed for the production and purification of recombinant phage proteins.

Thesis embargoed until 31 December 2022.

Date of Award	Dec 2021
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Katrina Campbell (Supervisor), Irene R. Grant (Supervisor) & Olivia McAuliffe (Supervisor)