Characterisation of microbial intraspecies variability in infections: an opportunity for improved treatment of polymicrobial diseases

Fungal-bacterial infections (FBI), such as those caused by the fungus Candida albicans and the bacteria Staphylococcus aureus, are recognised as an urgent threat to human health. They are the most common agents co- isolated from biofilm-associated diseases such as skin infections and ventilator-associated pneumonia. To date, the interaction between both microorganisms within these biofilms has been described as synergistic, although data from our laboratory observed antagonistic interactions. The degree of synergism between C. albicans and S. aureus is dependent on the patient-derived S. aureus strain. As a result of bacterial intraspecies variability, the composition of the different biofilms varied greatly. Consequently, synergistic interactions promoted survival of C. albicans in the presence of antifungal drugs and a dampened innate immune response when compared to antagonistic interactions. We hypothesize that differences in C. albicans – S. aureus biofilms, resulting from S. aureus intra-species variability, will result in biomarkers, secondary metabolites and immunotherapy targets that are unique to these biofilm-associated variations and that could be exploited for future treatment options. The aim of this project is therefore to dissect the molecular mechanisms underlying bacterial intraspecies variability in synergistic and antagonistic interactions with C. albicans within biofilms a) to identify genetic targets and biomarkers in the different biofilms through performing RNA-sequencing, b) to uncover secondary metabolites secreted by either microorganism in the different biofilms by mass spectrometry and test their antimicrobial potential, c) to further unravel immune responses to co-infections of C. albicans with synergistic and antagonistic S. aureus strains using flow cytometry techniques.

Applicants should have a first or upper second-class honours degree in an appropriate subject or a relevant Masters qualification.

If your first language is not English, you will need to meet the minimum English requirements for the programme, IELTS Academic score of 6.5 (with no less than 5.5 in each component test area) or equivalent.

The studentship is supported for 3 years and includes full home tuition fees plus a stipend of £18,655 per annum 2024/25 rate (2025/26 rates TBC). The studentship will only fully fund those applicants who are eligible for Home fees with relevant qualifications. Applicants normally required to cover International fees will have to cover the difference between the Home and the International tuition fee rates.

There is no additional funding available to cover NHS Immigration Health Surcharge (IHS) costs, visa costs, flights etc.

NB: The studentship is supported for three years of the four-year registration period. The fourth year is a self-funded ‘writing-up’ year.

If you wish to discuss this project further informally, please contact Dr Laure Ries by email: laure.ries@plymouth.ac.uk.

Please see our apply for a postgraduate research programme page for a list of supporting documents to upload with your application.

For more information on the admissions process generally, please visit our apply for a postgraduate research programme page or contact the Doctoral College .

Shortlisted candidates will be invited for interview 5–9 May 2025. We regret that we may not be able to respond to all applications. Applicants who have not received a response within six weeks of the closing date should consider their application has been unsuccessful on this occasion.