Deciphering receptor-binding proteins of phage tournay and driving phage evolutionary adaptation for anaerobic infection of staphylococcus aureus

Details

Supervisors

Gillis, Annika

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

enThe increasing prevalence of antibiotic-resistant bacteria represents a major global health challenge and highlights the urgent need for alternative therapeutic strategies. In this context, phages have re-emerged as promising antibacterial agents because of their specificity and efficacy against bacterial pathogens such as Staphylococcus aureus. However, improving phage-based therapies requires a better understanding of phage-host interactions and factors influencing phage activity under clinically relevant conditions, including anaerobic environments. This project aimed to investigate two complementary aspects of phage biology. First, the molecular mechanisms underlying the interaction between the Kayvirus phage Tournay and S. aureus DPC5246 were explored, with a particular focus on the role of wall teichoic acids in phage recognition and adsorption. Second, the adaptive potential of Kayvirus phage K under anaerobic conditions was evaluated through a phage training approach. To achieve these objectives, a bacterial mutant with modified wall teichoic acids glycosylation patterns was generated, and receptor-binding proteins from phage Tournay fused to GFP were produced. Complementary approaches, including fluorescence microscopy, phage-infectivity [spot-test] assay and the generation of resistant mutants, were used to characterise phage-host interactions and investigate resistance mechanisms. Evolution experiments were also performed to promote phage adaptation under anaerobic conditions. The results of this work confirms that wall teichoic acids glycosylation plays an important role in receptor accessibility and phage recognition. In addition, resistant mutants that did not bind to the bacterial receptor displayed heterogeneous phenotypes, indicating that multiple mechanisms may contribute to phage resistance. Although phage training under anaerobic conditions could not be successfully maintained over successive passages, the observations obtained provided valuable insight into factors potentially affecting phage amplification and adaptation under anaerobic conditions. Overall, this work highlights the complexity of phage-host interactions and provides a foundation for future studies aimed at improving phage efficacy for therapeutic applications.