Unravelling the Molecular Mechanisms Behind Prs-Mediated Antibiotic Tolerance

The aim of this study is to further our understanding of the mechanistic basis and clinical significance of antibiotic tolerance, a bacterial phenomenon that contributes to persistent and recurrent infections.

Tolerance describes the ability of a bacterium to survive transient exposure to an otherwise lethal concentration of antibiotic without exhibiting resistance.

Tolerant bacteria die slower than non-tolerant bacteria, meaning that longer antibiotic exposures are required to achieve complete killing (hence the association with persistent/recurrent infections). We have recently observed that a clinical isolate of Staphylococcus aureus exhibits tolerance due to a mutation in Prs.

Prs mutations have also been detected in in vitro-evolved strains of S. aureus and Escherichia coli under antibiotic selection. Prs synthesises the metabolite PRPP that feeds into purine synthesis.

We hypothesise that these mutations reduce the activity of Prs and limit the supply of PRPP, thereby reducing the GTP pool and phenocopying the effects of stringent response activation (we have previously identified stringent response activation as a mechanism of tolerance in clinical isolates).

Here, we will attempt to unravel the molecular mechanisms behind Prs-mediated tolerance using enzymology, structural biology, analytical biochemistry, transcriptomics and bacterial genetics.

We will also assess the impact of Prs mutations on antibiotic treatment outcomes in a Galleria mellonella infection model.

This will represent the first experimental in vivo evaluation of tolerance and its consequences for antibiotic efficacy.

Overall, this study will provide much-needed insight into the underappreciated phenomenon of tolerance, and support efforts to develop anti-tolerance agents and alternative treatment strategies.