Ryan Marsh

Senior Research Assistant

School: Geography and Natural Sciences

University of Sheffield (2014-2019)

Whilst studying Biomedical Science, I was introduced to cystic fibrosis (CF) and worked on the activation of the CFTR protein in 16HBE14o- human bronchial epithelial cell line to model respiratory ion transport dynamics utilising classical cell electrophysiology approaches.

My interest in CF further developed during my study of Molecular Medicine, where I investigated the role of virulence factors across prominent CF respiratory pathogens. Specifically, this was the characterisation of tonB mutants in Gram-negative bacteria such as Burkholderia cenocepacia with respect to environmental iron acquisition.

Manchester Metropolitan University (2019-2023)

I then decided to study the role of complex microbial communities upon the health of people with CF through a CF Trust-funded Venture & Innovation Award (VIA) at Manchester Metropolitan University under the supervision of Professor Chris van der Gast. Specifically, this entailed research into the gut microbiome and its relationships with gut function and physiology in CF, including the impact of medications and antibiotics. Here, I developed GC-MS approaches to quantify faecal short-chain fatty acids and further integrated these additional ‘omics’ techniques to help answer our research questions.

In collaboration with the University of Nottingham, I delivered world-first research detailing the impact of extended CFTR modulator (elexacaftor-tezacaftor-ivacaftor) usage on the gut microbiome, including relationships with oro-caecal transit, small-bowel water content, and colonic volumes.

Northumbria Univeristy (2023-present)

In my current CF Trust-funded role as part of the GRAMPUS-CF SRC, I continue to investigate the complex interplay between gut microbiome and host in CF under the guidance of Professor Chris van der Gast. Specifically, GRAMPUS-CF aims to identify the mechanism’s that underpin persistent intestinal symptoms and abnormalities in the CF population. To understand the potential role of the microbiome, I collaborate with other experts at Northumbria University to employ metagenomics, metabolomics, and lipidomics, combined with patient clinical data across multivariate statistical approaches in pursuit of these aims.

Email Ryan

Research Themes and Scholarly Interests

I am interested in microbiome-host relationships that underpin intestinal diseases. Specifically, this involves research into the cystic fibrosis (CF) gut microbiome, to understand how gut microbiome dysbiosis further compounds intestinal abnormalities at the site of the GI tract and how this relates to gut symptoms frequently experienced by the CF community.

To answer these research questions, I employ multi-omics approaches and integrate phenotypic clinical data through multivariate statistics to model these intricate relationships. I leverage the use of in vitro models resembling the CF intestinal tract to further understand the impacts of CF-associated factors such as diet, antibiotics, medications, and inflammatory markers upon bacterial communities, including functional consequences that could impact the host response.

Find out more about my work here: ResearchGate

Key Publications

Please visit the Pure Research Information Portal for further information
Cystic fibrosis related diabetes has a distinct gut microbiome dysbiosis, Marsh, R., Sills, D., Saumtally, H., Tricker, J., Cheung, W., Arends, D., Párniczky, A., Ocskay, K., Peckham, D., Spiller, R., Marciani, L., Downey, D., Stewart, I., Monaghan, T., Smyth, A., Rivett, D., van der Gast, C. Jun 2026, In: Journal of Cystic Fibrosis
Remodelling of cystic fibrosis respiratory microbiota in response to extended elexacaftor–tezacaftor–ivacaftor therapy, Gavillet, H., Hatfield, L., Hardman, M., Marsh, R., Einarsson, G., Thornton, C., Parkins, M., Duckers, J., Bomberger, J., Hilliam, Y., Lee, S., Lord, R., Jones, A., Horsley, A., Daniels, T., Teneback, C., Rivett, D., van der Gast, C. 3 Aug 2026, In: Microbiome
The gut microbiome: Recent findings and future opportunities in cystic fibrosis, Marsh, R., Tricker, J., Delhaes, L., Bomberger, J., van der Gast, C. 9 May 2026, In: Journal of Cystic Fibrosis
Towards a gut-lung axis role in pwCF on CFTR modulators: rationale, clinical evidence and perspectives, Lefranc, M., Ramel, E., Marsh, R., Tricker, J., van der Gast, C., Bomberger, J., Delhaes, L. 13 May 2026, In: Journal of Cystic Fibrosis
Investigating microbiota differences across chronic pancreatitis, influenced by lifestyle and genetic determinants, Ahmed, A., Rajai, A., Fullwood, C., Rivett, D., McLaughlin, J., van der Gast, C., Marsh, R. 21 Oct 2025, In: BMC Gastroenterology
Species turnover within cystic fibrosis lung microbiota is indicative of acute pulmonary exacerbation onset, Cuthbertson, L., Hatfield, L., Gavillet, H., Hardman, M., Marsh, R., Rivett, D., van der Gast, C. 7 Jun 2025, In: Microbiome
WS04.02: Gut microbiota-metabolome relationships across CFTR modulator usage: preliminary findings from the GRAMPUS-CF study, Marsh, R., Cheung, W., Arends, D., Sills, D., Rivett, D., Smyth, A., van der Gast, C. Jun 2025, In: Journal of Cystic Fibrosis
Impact of extended Elexacaftor/Tezacaftor/Ivacaftor therapy on the gut microbiome in cystic fibrosis, Marsh, R., Dos Santos, C., Yule, A., Dellschaft, N., Hoad, C., Ng, C., Major, G., Smyth, A., Rivett, D., van der Gast, C. 1 Sep 2024, In: Journal of Cystic Fibrosis
Tezacaftor/Ivacaftor therapy has negligible effects on the cystic fibrosis gut microbiome, Marsh, R., Dos Santos, C., Hanson, L., Ng, C., Major, G., Smyth, A., Rivett, D., van der Gast, C. 17 Oct 2023, In: Microbiology spectrum
Intestinal function and transit associate with gut microbiota dysbiosis in cystic fibrosis, Marsh, R., Gavillet, H., Hanson, L., Ng, C., Mitchell-Whyte, M., Major, G., Smyth, A., Rivett, D., van der Gast, C. 1 May 2022, In: Journal of Cystic Fibrosis