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Julian Marchesi

Professor Julian Marchesi

Honorary Professor

School of Biosciences

Sir Martin Evans Building, Room Cardiff School of Biosciences, Main Building, Museum Avenue, Cardiff, CF10 3AT, Museum Avenue, Cardiff, CF10 3AX
Available for postgraduate supervision


The human microbiome has recently been found to be an integral part of human biology.  For many years it was viewed as a source of infection, but now we know it is an essential component of the host and needed for normal development and function.  My research since 2001 has focused on understanding the roles that the bacterial component of the microbiome plays in maintaining health and promoting diseases.

Research overview

  • Microbiology of the gut, skin, lung and female reproductive system
  • Host-microbes interactions in the gut, lungs, skin and female reproductive system
  • Impact of bacterial produced metabolites and proteins in the gut and female reproductive system
  • Bioactive and biocatalytic agents from the human microbiome using functional metagenomics
  • Using metataxonomics (16S rRNA gene profiles) and metagenomics to explore the human microbiome in health and disease
  • The role of the microbiome in cancer, inflammatory bowel disease, obesity, liver disease, pre-term labour and autoimmune diseases
  • How the microbiome interacts with the diet to drive health.
  • Understanding the role of the gut microbiota in controlling infections in the gut and providing colonization resistance.

Microbiomes, Microbes and Informatics

The Marchesi group is part of the recently formed Microbiomes, Microbes and Informatics (MMI) group (webpage underdevelopment). The MMI group currently comprises the research groups of Thomas Connor, Esh Mahenthiralingam, Julian Marchesi and Andrew Weightman, and has over 25 active research staff and postgraduate students.

The MMI group are highly research active generating over £3.5 million in grant income between 2010 and 2017, and publishing extensively in top journals (cumulative h index > 150, > 400 publications, and > 25,000; source

The four current MMI staff recently moved (June 2017) to a single shared location within a new £1.6 million refurbished area of the Sir Martin Evans Building. This comprises a large class II certified research laboratory, equipment and tissue culture rooms, a group office area and academic offices. The MMI group welcomes approaches by potential fellowship applicants and funded PhD students to host their research and expand our strategic research on Microbiomes, Microbes and Informatics.

Interested in joining my lab as a self-funded post-graduate student or a postdoc/fellow?  Please contact me by email.


The main focus of the research in my group is to determine the role gut microbes play in host development, health and disease. We have been using a variety of molecular approached to investigate both the culturable and unculturable fractions of the gut microbiota, including microbiomics (16S rRNA gene clone libraries, DGGE), functional metagenomics and metabonomics.

Additionally we are also exploring the potential of the gut  associated microbes to provide novel bioactive and biocatalytic agents which can be used to treat disorders of the gut and the host, for example, Clostridium difficile associated diseases, inflammatory bowel disease and colorectal cancer.


After graduating from Cardiff University I started work on looking at the impact of genetically modified microbes on natural ecosystems. At this point I developed an interest in the contribution of uncultured microbes to the maintenance and function of "natural" ecosystems i.e. molecular microbial ecology.  After this research position I continued to use molecular biological methods to investigate microbes in the deep biosphere ecosystem which exists below the sea-floor and developed molecular methods to investigate methane producing bacteria in this ecosystem.

I followed this work with a Wellcome Trust Fellowship and extended my molecular microbial ecology interest to investigate, using culture independent methods, the diversity and distribution of genes involved in biodegradation of priority pollutants. It was during this period that I started turning my attention to using these molecular methods to explore the unculturable bacteria and their involvement in the human ecosystem.

I obtained a Lectureship in the Department of Microbiology, University College Cork (UCC) and this provided me with the opportunity to investigate the contribution microbes make to gastrointestinal tract function.  In UCC my group investigated the human gut ecosystem in health and disease and used molecular methods to understand how bacteria contribute to the key functions which are found in human GI tracts.

My current research interest is to continue this work in Cardiff and to further shed light on the contributions and role the human microbiome plays in health and disease.  The human microbiome consists of all the microbial genomes which are found in the human ecosystem.  The main fraction resides in the gastrointestinal tract and this collection of genetic information contains many functions which are able to influence the host's own metabolism.  In fact the combined metabolic functions of these microbes are equivalent to that of the liver and we are now considering the gut microbiome as a virtual organ.  But unlike any conventional organ the range of functions are very dynamic and can be perturbed easily.  The gut microbiome has been implicated in many health and disease processes including obesity, non-alcoholic fatty liver disease and several atopic diseases.  Since this collection of microbes varies from one individual to another there exists the possibility that different individuals are being affected differently by their microbiome.