A Porphyromonas gingivalis genetic locus encoding a heme transport system

Porphyromonas gingivalis has been implicated in the onset and progression o f 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 mem brane receptor gene tlr. This gene was previously identified as a TonB-link ed adhesin gene tla and shown to be essential for growth at low concentrati ons of hemin. The tlr gene is immediately downstream of four open reading F rames (htrABCD) that encode a putative ATP binding cassette transport syste m with sequence similarlity to heme transport systems of other bacteria. An alysis of P. gingivalis W50 mRNA revealed that the htrABCD genes are cotran scribed similar to hemin transport genes of other bacteria.