Mechanisms of Oxidative Stress Resistance in Porphyromonas gingivalis W83

<p><em>Porphyromonas gingivalis</em>is one of the most important bacterial etiological agents involved in adult periodontitis. It possesses several virulence factors which aid in its persistence in the periodontal pocket leading to the development of some systemic illnesses. As an anaerobe, <em>P. gingivalis</em>must employ mechanisms to avoid oxidative stress generated by reactive oxygen species during phagocytosis, or the occasional exposure to air. Presently, only three proteins with antioxidant enzymatic function have been identified as playing a role in oxidative stress resistance in <em>P. gingivalis.</em> In this study, attention was focused on the alkyl hydroperoxidase subunit C <em>(ahpC)</em>and bacterioferritin comigratory protein <em>(bcp)</em> genes, DNA repair mechanisms and the unique hemin layer of <em>P. gingivalis. </em>We tested the physiological function of the isogenic <em>ahpC</em> and <em>bcp</em>mutants to hydrogen peroxide. When compared to the wild-type <em>P. gingivalis</em> W83, both the <em>ahpC</em> and <em>bcp</em>isogenic mutants, designated FLL141 and FLL301 respectively, demonstrated a greater sensitivity to hydrogen peroxide. However when tested in an animal model of virulence, the virulence potential of these mutants was similar when compared to the wild-type. These data suggest an involvement of these genes in oxidative stress protection but not in virulence. Further, recent reports indicated that the hemin layer was involved in protecting <em>P. gingivalis</em>from hydrogen peroxide. Consequently, the hypothesis that a non-pigmented strain of <em>P. gingivalis</em>, FLL92, would be more sensitive to oxidative stress than the wild-type <em>P. gingivalis</em>W83 was investigated. </p> <p>Interestingly, when compared to the parent strain, FLL92 was more resistant to hydrogen peroxide. As a result, the hypothesis that <em>P. gingivalis</em> FLL92 would incur more DNA damage than the wild-type was investigated. Data from these experiments demonstrated an increase in the oxidative DNA lesion 8-oxoguanine and its related enzymatic removal activity in <em>P. gingivalis</em> FLL92 in comparison with the parent strain. Additionally, a novel removal activity for 8-oxoguanine from duplex DNA was identified in <em>P. gingivalis</em> when compared to other oral anaerobes. Collectively, these data suggest that <em>P. gingivalis</em> W83 may utilize antioxidant enzymatic activity, the hemin layer and DNA repair enzymes as part of an intricate defense mechanism against oxidative stress.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Microbiology, Molecular Biology and Biochemistry

Year

2004

Author dc:creator

• Johnson, Neal Antonio

Contributors dc:contributor

• Hansel Fletcher
• Carlos Casiano
• Alan Escher
• James Kettering
• Lawrence C. Sowers

• Microbiology
• Porphyromonas gingivalis -- enzymology; Porphyromonas gingivalis -- genetics; Porphyromonas gingivalis -- pathogenicity; Oxidative Stress; Virulence; Gene Expression Regulation, Bacterial; Periodontitis -- microbiology.

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/635

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1760