Investigating Pseudomonas aeruginosa physiology and the impact of pathoadaptive mutations, in a polymicrobial airway environment

BBSRC strategic theme: Bioscience for an integrated understanding of health

The airways of people with cystic fibrosis (CF) are often colonised by a diverse "zoo" of microbes, especially during their early and teenage years. These polymicrobial communities have historically proven difficult to recapitulate in the laboratory environment, so, until now, most research has involved monoculture of key pathogens such as Pseudomonas aeruginosa. It is becoming increasingly clear, however, that pathogens in multi-species systems often behave radically differently than when grown in pure axenic cultures, and, as such, recent years have seen a growing interest in efforts to recapitulate the complex CF microbiota in vitro.

The Welch Lab has developed an in vitro laboratory model that accurately captures the long-term stability of the polymicrobial community present in CF airways. In brief, the setup consists of a continuous flow bioreactor in which the rate of fluid - specifically, artificial sputum media - replacement reflects that seen in the airways. The current model incorporates three major CF-associated pathogens: P. aeruginosa, Staphylococcus aureus, and Candida albicans. This system has opened new possibilities for interrogation of the biology of CF-associated polymicrobial airway infections, and has already yielded some intriguing new insights.

In this project, I will introduce other common CF-associated pathogens into the in vitro model system, alongside the current three, for example: Haemophilus influenzae, Rothia mucilaginosa, and Streptococcus milleri. I will then use this "improved" model system to examine the impacts of the presence of P. aeruginosa mutants in the polymicrobial community. The P. aeruginosa population observed in CF airway infections is not homogenous, with mutant variants frequently observed. Loss-of-function mutations in certain genes are commonly over-represented in CF, indicating they may confer increased fitness in this environment;...