A Porphyromonas gingivalis genetic locus encoding a heme transport system

Porphyromonas gingivalis has been implicated in the onset and progression of periodontitis and the availability of hemin for in vitro growth has been associated with virulence of the bacterium in animal models. We report here the cloning and sequence analysis of a P. gingivalis TonB-linked outer membrane receptor gene tlr. This gene was previously identified as a TonB-linked adhesin gene tla and shown to be essential for growth at low concentrations of hemin. The tlr gene is immediately downstream of four open reading frames (htrABCD) that encode a putative ATP binding cassette transport system with sequence similarlity to heme transport systems of other bacteria. Analysis of P. gingivalis W50 mRNA revealed that the htrABCD genes are cotranscribed similar to hemin transport genes of other bacteria.