MRC DiMeN Doctoral Training Partnership: Migration of Pseudomonas aeruginosa towards antibiotics: mechanisms and consequences

Description

Background:

P.aeruginosa is a globally significant “priority” bacterial pathogen (WHO) that causes life-threatening antibiotic-resistant infections. Whilst P.aeruginosa is widely studied in liquid-culture, most cells in natural and clinical settings live within surface-attached biofilms. Whilst liquid-borne bacteria swim away from harmful chemicals, we recently found that surface-attached P.aeruginosa counter-intuitively crawls towards – rather than away from – clinical antibiotics, a novel behaviour we call ‘antibiotic taxis’^[1,2]. This exciting discovery raises many new questions about the genetic and behavioural mechanisms underlying this response and whether it allows cells to acquire resistance.

We speculate that antibiotic taxis enables P.aeruginosa to respond to antibiotics produced by competing bacteria by navigating directly towards them in a counterattack manoeuvre. For example, surface-attached P.aeruginosa has been found to migrate towards toxins produced by Staphylococcus aureus, a species with which it commonly co-infects cystic fibrosis patients^[3]. However, the mechanistic basis of this response, and how it facilitates competitive interactions between co-infecting pathogens, remains unknown. In addition, little is known about the implications of antibiotic taxis in the context of clinical antibiotics and how it contributes to the prevalence of antibiotic resistance in P.aeruginosa. This project will begin to address these questions, developing a fundamentally new understanding of how bacteria interact with both synthetic clinical antibiotics and anti-microbials produced by competing strains during co-infection, potentially shedding new light on how bacteria acquire antibiotic resistance.

Objective 1:

How does antibiotic taxis facilitate resistance evolution? We have previously studied antibiotic taxis using steep gradients that drive strong responses, but these ultimately kill responding cells. Here, we will use microfluidics to generate realistic antibiotic landscapes to resolve how movement towards progressively higher antibiotic concentrations might facilitate resistance evolution over multiple days.

Objective 2:

How do cells sense antibiotic gradients? We found that the Pil-Chp signalling pathway regulates chemotaxis in surface-attached P.aeruginosa^[4,5]. However, the receptor associated with this pathway is not required for antibiotic taxis, implicating a novel sensing mechanism. We will resolve the molecular components underpinning antibiotic taxis using mutants and sophisticated cell-tracking tools to analyse their behaviour.

Objective 3:

What attracts P.aeruginosa towards S.aureus colonies? Bacteria secrete diverse compounds that could impact motility. Using microfluidic assays, we will identify compounds driving P.aeruginosa attraction to S.aureus colonies (including recently implicated toxins) and resolve the behavioural/genetic mechanisms involved.

Research approach:

These objectives require an inherently interdisciplinary and collaborative approach: our supervisors (Dr Jamie Wheeler (University of Liverpool), Dr William Durham, (https://microbialphysicsgroup.sites.sheffield.ac.uk/people) and Prof. Aras Kadioglu (https://www.liverpool.ac.uk/people/aras-kadioglu)) combine expertise across molecular microbiology, microfluidics, automated-microscopy, massively parallel cell-tracking and immunology. The successful student will receive extensive training across these disciplines, working with state-of-the-art tools. For instance, our supervisory team has been directly involved in the development of novel technologies (including 3D-printed fluid-walled microfluidic devices^[2,6] and custom cell-tracking software^[7]) that have opened new ways of studying bacteria.

Together, we adopt a strongly collaborative and inclusive research approach fostering creativity, cooperation and student-led networking opportunities. The successful student will therefore be well equipped for a future career in cutting-edge research, using diverse tools to answer fundamental problems in biology.

Benefits of being in the DiMeN DTP:

This project is part of the Discovery Medicine North Doctoral Training Partnership (DiMeN DTP), a diverse community of PhD students across the North of England researching the major health problems facing the world today. Our partner institutions (Universities of Leeds, Liverpool, Newcastle, York and Sheffield) are internationally recognised as centres of research excellence and can offer you access to state-of-the-art facilities to deliver high impact research.

We are very proud of our student-centred ethos and committed to supporting you throughout your PhD. As part of the DTP, we offer bespoke training in key skills sought after in early career researchers, as well as opportunities to broaden your career horizons in a range of non-academic sectors.

Being funded by the MRC means you can access additional funding for research placements, training opportunities or internships in science policy, science communication and beyond. Further information on the programme and how to apply can be found on our website:

https://www.dimen.org.uk/