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Modulation of the human gut microbiome in order to promote host health and well-being

Evans, James 2014. Modulation of the human gut microbiome in order to promote host health and well-being. PhD Thesis, Cardiff University.
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Background. Numerous studies into the effect of probiotic supplementation in the infirm have been carried out. However, research into the effect of long-term probiotic supplementation in healthy individuals is lacking. With this in mind the PROHEMI study, a randomized, double-blinded, multi-centre and long-term (6 months) probiotic feeding study in healthy males was designed and carried out. Through the use of varied culture dependent and independent techniques, the effects of long-term probiotic consumption were researched. In addition, a study into the effect of freezing faecal material on its bacterial composition was also carried out. Results. Through a community fingerprinting technique and next generation sequencing it was shown that the distal gut bacterial community is unaffected by probiotic supplementation. Functional screening of faecal material showed a reduction in bacteria expressing protease activity when probiotic supplementation began. In addition, bacteria expressing β-galactosidase and β-glucuronidase activity increased during probiotic supplementation. Metabonomic analysis showed no difference in metabolite profiles attributable to probiotic supplementation. However, differences between the gut bacterial community, metabonomic profiles, and bacteria expressing functions were observed between the two study centres. Freezing of faecal material at -20°C detrimentally affected its bacterial composition between 2 weeks and 3 month storage time-points. Significant reductions in the abundance of the Bacteroidetes phylum observed following 6 months of storage at -20°C. Conclusions. Long-term probiotic administration in healthy individuals did not seem to affect the distal gut bacterial community in these individuals and did not affect metabonomic profiles. However, some functions expressed by the resident distal gut bacterial community were significantly affected during probiotic supplementation. DNA extraction from faecal material should ideally be carried out from fresh samples. Failing this it is not recommended to store samples at -20°C for longer than 2 weeks prior to DNA extraction.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QR Microbiology
Uncontrolled Keywords: Gut microbiota; Probiotic Lactobacillus acidophilus; Length heterogeneity PCR; Next generation sequencing
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:40

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