The Noncontractile Phage Tail-like Bacterial Killing Nanomachines – Characterizing the Specificity Determinants of the F-Pyocins of Pseudomonas aeruginosa

The rise of antibiotic-resistant bacterial strains poses an enormous threat to our collective human existence; hence, there is a dire need to search for alternatives to current antibiotic treatment options. In this work, I characterized the non-contractile phage tail-like entities called F-pyocins. F-pyocins are high molecular weight bacteriocins resembling non-contractile bacteriophage tails such as E coli phage lambda of the Siphoviridae family. They are produced by many Pseudomonas aeruginosa strains and possess bactericidal activity against other strains of the same species. Structurally, F pyocins are differentiated into the tubular portion and the tail tip complex lying at the bottom of the tail. F-pyocins produced by different strains of Pseudomonas aeruginosa, share strong sequence similarities in the genes encoding the tubular portion, however, notable variability exists in the last six genes at the tail tip complex, collectively designated here as specificity genes. In this study, I differentiated F-pyocins into groups based on the sequence diversity in their specificity genes, which assort into two modules – modules 1 and 2, each comprising three genes. I showed that swapping module 2 from one F-pyocin to the other changes the killing spectrum of the chimeric F-pyocin to new P. aeruginosa strains. This is mediated by the interaction of the module 2 c-terminus with the LPS O-specific antigen (OSA) of the target P. aeruginosa strain. Module 1 on the other hand was shown to interact with target receptor moieties deeper within the LPS core implying that each module has selective specificity and that F-pyocins may have evolutionarily co-opted both modules to ensure the successful killing of their target P. aeruginosa strain. The plasticity of F-pyocins was further explored by engineering them with side fibre proteins from siphophage DMS3, which retargeted their bactericidal spectrum. Summing all my findings, I concluded by proposing the mechanism with which F-pyocins bind and kill susceptible P. aeruginosa strains. This study provides valuable insight into the specificity determinants of F-pyocins and how they interact with the bacterial surface, which further helps us to understand how they can be explored as potential alternatives to antibiotics.

Department dc:contributor.department

Molecular Genetics

Year dc:date.issued

2022

Author dc:creator

• Ojobor, Chidozie Donald

Advisor dc:contributor.advisor

• Davidson, Alan R

• Bacteriocin
• F-pyocin
• LPS
• Phage
• Pseudomonas aeruginosa
• Specificity genes

Handle dc:identifier.uri

http://hdl.handle.net/1807/125187

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/125187