Doctor of Philosophy in Microbiology and Immunology (PhD)
Impact of osmotic perturbations on the gut microbiota
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Probiotics have been identified as potential therapeutic vessels for numerous intestinal conditions, but we do not yet understand their ability to colonize a host, particularly one whose gut environment has been affected by disease. Physical factors are key in determining the ability of bacteria to survive and colonize within the gut and need to be investigated in the context of probiotic therapy. This project aims to characterize the strain-specific adaptability of commercially available probiotic strains to disease-relevant physical parameters – pH and osmolality. Different strains of lactic acid producing bacteria and Bifidobacterium spp. were isolated from ten commercially available probiotics and assessed for their growth in various pH and osmolality conditions and for their ability to impact their surrounding abiotic environment. We found that probiotic strains from the same phyla exhibit differential growth responses to high osmolality and low pH conditions, and we performed comparative genomic analysis to identify candidate genes involved in probiotic stress response. This study highlights the impact of biophysical parameters on commensal bacteria survival and helps to inform characteristics that are important for probiotic strains to establish sufficient viability in the dynamic gastrointestinal environment and will ultimately facilitate the development of other microbiota-based therapies.