In this episode, we go beyond genetic and molecular narratives of Parkinson’s disease to explore a bold new frontier: the role of the microbiome as a biomarker, bystander, or therapeutic target in cognitive decline. My guest today is Dr Frederick Clasen, Research Associate at the Centre for Host-Microbiome Interactions, Faculty of Dentistry, Oral & Craniofacial Sciences, King’s College London. Dr Clasen completed his undergraduate and master’s work in Bioinformatics and Biotechnology at the University of Pretoria before earning his PhD across the Francis Crick Institute and King’s College London, where he developed mathematical and genome-scale models of host and microbial metabolism.

Dr Clasen is first author on a landmark 2025 study published in Gut Microbes that used shotgun metagenomics and machine learning to map both oral and gut microbiome changes across healthy controls and Parkinson’s patients with varying degrees of cognitive impairment. Their work reveals that microbes — and specifically oral microbes translocating to the gut with enriched virulence factors — may be linked to Parkinson’s cognitive decline via an oral-gut-brain axis, offering not just associations but mechanistic hypotheses and potential biomarkers.

In this conversation we unpack:

• Why the microbiome may be more than a bystander in Parkinson’s disease
• What makes a microbial biomarker credible vs. noise
• How virulence factors and host metabolism may influence brain function
• What it takes to move from correlation to testable mechanism
• The real hurdles — and opportunities — for translating microbiome science into diagnostics and therapies

If you’re a scientist, clinician, founder, or investor curious about where biology meets translation, this episode will sharpen how you think about mechanism, de-risking, and what truly counts as a target in complex human disease.