Under Phage Pressure: Competition, Coexistence and Persistence in Polymicrobial Biofilms
Supervisors
Dr Giuseppina Mariano, School Infection of Immunity, University of Glasgow
Dr Suzanne Humprey, University of Strathclyde
Prof Donal Wall, School Infection of Immunity, University of Glasgow
Summary
Polymicrobial biofilms contain interacting bacterial species whose behaviour cannot be predicted from experiments on either species alone. This PhD will investigate how competition between Staphylococcus aureus and Pseudomonas aeruginosa interacts with bacteriophage predation to determine which species dominates, coexists or persists. The project will use an established in vitro ventilator-associated pneumonia biofilm model that captures the structured and oxygen-variable environment in which these organisms interact.
The student will first determine how strain background, starting abundance, colonisation order, nutrient availability and oxygen influence biofilm composition, bacterial physiology and spatial organisation. They will then examine whether growth in a polymicrobial community changes phage adsorption, replication, penetration or killing, and whether phage infection alters bacterial competitive behaviour. Finally, longitudinal experiments involving repeated biofilm formation and phage exposure will reveal how predation and the evolution of phage resistance reshape community composition over time.
The project offers broad training in polymicrobial biofilm models, species-specific viable counting, phage infection assays, bacterial genetic manipulation, confocal microscopy, transcriptional profiling, genome sequencing, bioinformatics and experimental evolution. Working across the Mariano, Humphrey and Wall groups, the student will connect molecular mechanisms with community-level outcomes and develop transferable skills in quantitative analysis, communication and research project management.