Iron-regulated outer membrane proteins in the periodontopathic bacterium, Bacteroides gingivalis

Hemin has been implicated in the pathogenesis of the oral pathogen, Bacteroides gingivalis. In order to elucidate the role of hemin (iron) in the growth and expression of outer membrane proteins, B. gingivalis strain W50 was grown with and without hemin to induce iron-limitation. Cells grew slower under iron stress and growth was completely inhibited in the absence of added hemin. The outer membrane protein profiles of B. gingivalis grown under iron-replete and iron-restricted conditions were studied by extrinsic radiolabelling with [125I] and polyacrylamide gel-electrophoresis. The induction of 10 surface proteins, with apparent molecular weights of 26, 29, 50, 56, 58, 60, 62, 71, 77, and 80 Kd, was observed in B. gingivalis grown under iron-restricted conditions. These proteins were repressed under iron-replete conditions. We postulate the involvement of the iron-regulated proteins in hemin uptake and virulence in B. gingivalis.