Storey, DouglasMehina, Nabiha2021-05-032021-05-032021-04-27Mehina, N. (2021). The influence of non-inhibitory concentrations of purified pyocin S2 on Pseudomonas aeruginosa isolates (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/113344Pseudomonas aeruginosa is an opportunistic pathogen whose impacts are primarily in clinical settings. It is possible for multiple P. aeruginosa strains to be involved in an infection and each strain can diverge into many morphotypes. Intraspecies interactions between strains and morphotypes leads to a complex environment involving both beneficial and antagonistic interactions. S-type pyocins are bacteriocin proteins produced by P. aeruginosa that can inhibit closely related strains. Previously, we observed a P. aeruginosa isolate using S-type pyocins to decrease the virulence of other isolates in a Drosophila melanogaster model. We have reason to believe that this decrease in virulence may not only be because of the direct inhibition of the target isolates but additionally from a reduction in their virulence factor production. As a result, we hypothesized that P. aeruginosa isolates use S- pyocins to influence the overall virulence of microbial communities by decreasing the virulence factor production of target bacteria. In the current study, we purified a DNase S-type pyocin, S2, and used a variety of virulence assays to show that subinhibitory concentrations of this pyocin alter the virulence factor production of target P. aeruginosa isolates. In doing so, we also demonstrated that the effects of S2 on virulence factor production can vary for different strains. We further explored the interactions between S2 and target bacteria by demonstrating how one isolate was able to gain resistance towards S2. Using genetic sequencing, we identified mutations that treatment with S2 is selecting for which may account for this resistance and explored how these changes may explain the altered virulence factor production displayed by this isolate. From the results of this work, we shed new light upon the reactions of surrounding strains to S2 production and proposed a potential novel mechanism of resistance against this pyocin.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.ScienceMicrobiologyMolecularBacteriaPseudomonas aeruginosaVirulenceBacteriocinSubinhibitoryInterstrain interactionsPyocinPyocin S2ResistanceEducation--SciencesMicrobiologyBiology--Molecularmaster thesis10.11575/PRISM/38808