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Title: Characterisation of the human intestinal microbiota based on community cellular fatty acid analysis and ribosomal RNA measurements
Author: Hopkins, M. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1999
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Chemostat studies were undertaken to validate the correlation between bacterial growth rate and 16S ribosomal RNA content for intestinal isolates, and also to identify potential 'signature' cellular fatty acids (CFA) for use as markers of bacterial community structure. These two methods were then used, in conjunction with traditional techniques, to investigate changes in the human colonic microflora associated with carbohydrate metabolism, antibiotic administration, and the ageing process. Short chain carbohydrates (SCC) were used to manipulate the composition and activities of the intestinal microbiota. They showed considerable potential as prophylactic agents in the prevention C. difficile infection. Viable count and 16S rRNA methodologies indicated that these carbohydrates predominantly stimulated bifidobacteria, although the metabolism of other bacterial genera could be affected, and the suppressive effect they induced against C. difficile was not limited to a specific species or genus. However, administration of SCC to patients undergoing antibiotic therapy could result in further impairment of colonisation resistance, with more fermentable carbohydrates, and broad spectrum antibiotics being of highest risk. Bifidobacteria were found to exhibit SCC substrate preferences when growing as part of the normal colonic microflora, which could have important consequences if a particular bacterial strain is to be targeted, such as during probiotic or prebiotic therapy. In conclusion, CFA analysis was effective in detecting differences between environmental samples, although careful consideration is needed to attribute these changes to an altered bacterial community structure rather than modification of the composition of bacterial membranes in stable populations. Viable count methodology proved advantageous for analysing inhibition of bacterial populations, whilst 16S rRNA analysis was the technique of choice for investigating metabolically active samples since it precludes the subjective nature of bacterial identification.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available