Elucidating the complexity and workings of the gut microbiota in mitochondrial disease provides a unique approach and deeper understanding of the biology in general, which is currently lacking in primary mitochondrial disorders. This research will contribute to the gut microbiome field and provide a novel insight into the complex microbe:microbe and microbiota-host interactions. The new insights generated here will provide the foundation for interventional studies aimed at manipulating the gut microbiome and relieving disease burden in patients with mitochondrial disease and potentially diseases associated with mitochondrial dysfunction, such as obesity, diabetes and neuro-degenerative disorders such as dementia and Parkinson's disease.