Polyphasic characterisation of the human oral microbiome

Haghegh, AY

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.

Citation

Haghegh, A. (in press). Polyphasic characterisation of the human oral microbiome. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Acceptance Date: Jun 29, 2015
• Deposit Date: Nov 9, 2015
• Publicly Available Date: Nov 9, 2015