Date on Master's Thesis/Doctoral Dissertation

5-2013

Document Type

Master's Thesis

Degree Name

M.S.

Department

Oral Biology

Committee Chair

Scott, David Albert

Author's Keywords

Porphyromonas gingivalis

Subject

Porphyromonas gingivalis--Effect of tobacco on; Tobacco--Physiological effect; Tobacco--Toxicology; Teeth--Diseases

Abstract

P. gingivalis is an opportunistic, anaerobic, Gram-negative oral pathogen strongly implicated in the pathogenesis of periodontal diseases. Clinical isolates of P. gingivalis exhibit great genetic diversity. Tobacco smoking greatly increases the risk of P. gingivalis infection. Furthermore, cigarette smoke extract (CSE) is an environmental stressor for P. gingivalis, differentially regulating multiple genes including ones that encode proteins involved in DNA translocation, replication and repair. Therefore, we hypothesized that CSE exposure would promote genomic instability in this important periodontal and systemic pathogen, which may contribute to increased virulence. P. gingivalis W83 was passaged 50 times in CSE-conditioned medium after which, genomic DNA was extracted and whole-genome sequencing was employed to identify any chromosomal alterations induced by CSE compared to un-exposed controls. Whole genome sequencing identified 22 CSE-induced point mutations (p < 0.05), 17 or which were confirmed as well as significant allelic variance (p < 0.001) in CSE versus control samples. Our results indicate that CSE exposure promotes genetic diversity in a laboratory strain of P. gingivalis. Should this phenomenon occur in vivo, tobacco smoke could promote bacterial evolution and, thus, contribute to the emergence of more virulent strains in this key periodontal pathogen, which may infect smokers and non-smokers alike.

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