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Polyphasic characterisation of the human oral microbiome

Haghegh, AY 2015, Polyphasic characterisation of the human oral microbiome , MSc by research thesis, University of Salford.

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Abstract

The oral cavity supports a complex and finely balanced consortia of microbial species, many of which co-operate within highly structured biofilm communities. Given the importance of this microbiome in oral disease, considerable scientific effort has been put into surveying its diversity, determining the nature of interactions between its members, and exploring its determinants. This dissertation addressed each of these areas; the three principal objectives were (1) to assess microbial diversity in the mouth using culture-based methods, (2) to use next-generation sequencing technologies to explore person-to-person and temporal variation in oral microbiome composition, and (3) to use an in vitro model system to analyse variation in the biofilm forming capacity of members of the oral microbiome. Objective 1: Samples of the microbiome were collected from one individual and plated onto a range of different axenic media, incubated under a range of different conditions. The diversity of isolates obtained was assessed on the basis of classical phenotypic characteristics and by using partial 16S rDNA sequence comparison. Twelve species were identified, all of which were well-recognised members of the oral microbiota. Objective 2: Next-generation sequencing was performed on 16S rDNA fragments amplified from plaque samples were collected from the oral cavity of three healthy adult human volunteers each month for a period of eight months. A wide diversity of OTUs was detected in all samples that could be delineated into 13 phyla and 48 families. 60 OTUs could be identified at the species level. As expected, general linear models revealed statistically significant variation among the OTUs present in different individuals and within individuals over time. Objective 3: Fourteen different oral streptococci strains were screened for biofilm formation using the established microtitre plate biofilm assay. The results of this study were inconsistent but it appeared that most strains best formed biofilms after about four days of incubation, and by day seven, bacteria had died. Optimisation of this technique is required. The results of this dissertation add to current knowledge about the diversity and dynamics of the human oral microbiome. This study has also obtained a set of lowpassage isolates of various members of the human microbiome and has begun to optimise an in vitro biofilm assay. Together, these will provide a useful resource for future exploration of the contribution of individual bacterial species to human oral biofilm infrastructure.

Item Type: Thesis (MSc by research)
Themes: Built and Human Environment
Health and Wellbeing
Funders: Non funded research
Depositing User: AY Haghegh
Date Deposited: 09 Nov 2015 15:18
Last Modified: 30 Nov 2015 23:53
URI: http://usir.salford.ac.uk/id/eprint/35744

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