Date of Award

Spring 1-1-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Norman Pace

Second Advisor

Kenneth Krauter

Third Advisor

Matthew B. McQueen

Fourth Advisor

Matthew C. Keller

Fifth Advisor

Robin D. Dowell

Abstract

Oral bacterial communities have an influence on human oral and systemic health. Variation in the presence and abundance of these communities between individuals has been demonstrated, but it is unclear what factors drive these variations. This dissertation analyzed the influence of host genetics, temporal changes, and environmental variables such as cohabitation and substance use, on the oral microbiota via a culture-independent approach.

A portion of the bacterial small ribosomal subunit (16S rRNA genes) were PCR amplified and subjected to 454 pyrosequencing from banked saliva samples derived from various studies of the Institute of Behavioral Genetics at the University of Colorado. Sequences were analyzed with QIIME, a software package for microbial analysis, in order to assess taxonomy and diversity differences. A commonly shared group of eight oral genera was identified. A longitudinal twin study design (age 12, 17 and 22) of 264 saliva samples obtained from 107 individuals revealed no differences between monozygotic (n=27) and dizygotic (n=18) twin pairs, which suggests a low influence of heritability. Intra-individual stability over two five year spans during adolescence and young adulthood was observed and twins were not significantly different from their co-twin during this time period. Cohabitation was a driving factor of microbiota similarity as individuals at age 22, following likely departure from shared environment, showed increased diversity compared to earlier time points when they lived together. Furthermore, several bacterial families changed significantly in abundance with age during adolescence. In addition, a second study of 210 individuals (aged 12 to 65) demonstrated an increasing dissimilarity based on age and smoking. The presence and abundance of a number of bacterial genera decreased with age and smoking, while potential oral pathogens increased.

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