Date of Award
Summer 2024
Degree Type
Thesis
Degree Name
Master of Science in Integrative Biology (MSIB)
Department
Department of Molecular and Cellular Biology
Committee Chair/First Advisor
Dr. Jean Lu
Second Advisor
Dr. Melanie Griffin
Third Advisor
Dr. Whitney Preisser
Abstract
Pseudomonas aeruginosa are prevalent opportunistic bacterial pathogens that cause nosocomial infections in at-risk individuals. The rise of multidrug-resistant P. aeruginosa poses an immense threat to hospitals. Additionally, P. aeruginosa are common food spoilage organisms that contribute to food waste. Alternative effective treatment methods are needed to improve public health and reduce food waste. Recent studies have shown that bacteriophages, viruses that only kill host-specific bacteria, are promising alternatives. This study characterizes two lytic P. aeruginosa phages, ΦPa-C and ΦPa-Tc, and evaluates their efficacy against P. aeruginosa in two model food systems. The morphology, genome, structural proteins, host range, growth kinetics, and thermal stability of both phages were studied to determine their characteristics. Each phage’s efficacy was evaluated against its respective host at MOIs of 1, 10, and 100 in cucumber juice and beef broth. Based on their characteristics and efficacy against P. aeruginosa, the potential of each phage as a biocontrol agent was determined. ΦPa-C was determined to belong to the Siphoviridae family, while ΦPa-Tc belongs to the Myoviridae family. ΦPa-C and ΦPa-Tc were identified as genetically different phages with different structural proteins. ΦPa-C had a narrower host range than ΦPa-Tc. ΦPa-C and ΦPa-Tc exhibited latent periods of 10 and 5 min, respectively. ΦPa-C had a small burst size of 23 PFU per infected cell, while ΦPa-Tc had a large burst size of 204 PFU per infected cell. Both phages were sufficiently stable at 63°C and 72°C for application to foods before pasteurization. ΦPa-C caused an approximate 5-log reduction of the host concentration in cucumber juice, regardless of MOI, within four hours and beef broth at MOIs of 10 and 100 within six hours. ΦPa-Tc caused an approximate 5-log reduction of the host concentration in cucumber juice and beef broth within six hours at an MOI of 100. These results suggest ΦPa-C and ΦPa-Tc are effective biocontrol agents for reducing P. aeruginosa in food. More research is needed to evaluate their efficacy in animal models to determine their biocontrol potential in infections.