Date on Master's Thesis/Doctoral Dissertation

12-2012

Document Type

Master's Thesis

Degree Name

M.S.

Department

Oral Health and Rehabilitation

Committee Chair

Demuth, Donald R.

Author's Keywords

Aggregatibacter; Acquisition; Actinomycetemcomitans; Dental; Iron; Pathogen

Subject

Periodontitis; Iron--Health aspects; Iron in the body

Abstract

The dental pathogen A. actinomycetemcomitans, a Gram- negative organism, has been associated with aggressive forms of periodontitis. A. actinomycetemcomitans requires iron to grow. In the host, iron-binding proteins such as transferrin, lactoferrin, hemoglobin, and ferritin, maintain a low free-iron concentration. Microorganisms, however, have evolved complex systems to efficiently harvest iron. The iron acquisition systems encoded in the genome of A. actinomycetemcomitans are likely tailored towards the specific survival strategies needed to survive in the oral biofilm. The objectives of this project were to determine the growth of A. actinomycetemcomitans in different iron sources and to examine the expression of the various iron uptake systems encoded by this organism under these conditions. A. actinomycetemcomtians was grown in chemically defined media (CDM) with or without an iron chelator (dipyridyl (DIP), and supplemented with various iron forms to determine growth. The growth of A. actinomycetemcomitans was decreased in a dose-dependent manner when cultured in CDM without exogenous ferrous sulfate supplemented with DIP (CDIDIP). Growth of A. actinomycetemcomitans was restored most efficiently when CDMIDIP was supplemented with hemin, less so with ferric citrate, and ferric chloride, and not with ferrous sulfate. Using these growth conditions, we examined the differential regulation of the numerous iron uptake systems encoded III the A. actinomycetemcomitans genome.

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