IADR Abstract Archives

The Role of Fur in Modulating Aggregatibacter actinomycetemcomitans Defense Mechanisms

Objectives: Aggregatibacter actinomycetemcomitans (Aa) is an oral bacterium that causes aggressive periodontitis, and sometimes life-threatening extra-oral infections. In the oral cavity, the organism is exposed to variety of environmental stresses which may affect its ability to successful colonize. One of the few regulatory proteins identified in Aa to date is the ferric uptake regulator (Fur). The aim of this study was to examine the role of the Fur protein in protecting Aa against oxidative cell damage and growth at acidic pH.

Methods: To determine the role of Fur in oxidative stress, Aawt, Aafur- and AaMnR mutants were cultured in the presence of 0.02 mM and 0.5 mM paraquat. Cell density (OD600) was recorded after 16 hours. Strains cultured in the absence of paraquat were used as controls. To examine the effect of mutations in fur on the ability of cells to grow at acidic pH, Aawt, Aafur-, AaMnR mutants were grown in TSBYE at pH 5.0 - 7.3 in 0.2 increments until stationary phase was reached.

Results: Superoxide dismutase activity was decreased in the fur mutant strains compared to the wild type strain as indicated by greater sensitivity to the redox-cycling agent paraquat. Aafur- and AaMnR strains were unable to grow at pH 6.2 or lower. In contrast, the Aawt strain was able to grow as low as pH 5.4. The Aa wild type cells were able to adapt to a wider range of acidic pH than the fur mutant strains suggesting that Fur is involved in growth at acidic pH.

Conclusions: The Fur protein may contribute to Aa pathogenicity in vivo, by protecting the bacterium against oxygen radical-mediated host defenses and by facilitating growth at acidic pH, both of which are crucial factors in the microorganism's ability to colonize the human oral cavity and produce virulence factors. TG # DE007034


IADR/AADR/CADR General Session
2007 IADR/AADR/CADR General Session (New Orleans, Louisiana)
New Orleans, Louisiana
2007
59
Microbiology / Immunology and Infection Control
  • Lee, Kwi Yeon  ( State University of New York - Buffalo, Buffalo, NY, USA )
  • Jordan, Shawn F.  ( State University of New York - Buffalo, Buffalo, NY, USA )
  • Haraszthy, Violet I.  ( State University of New York - Buffalo, Buffalo, NY, USA )
    • Oral Session
    Aggregatibacter actinomycetemcomitans I
    03/21/2007