Identification of a two-component signal transduction system involved in fimbriation of Porphyromonas gingivalis

Porphyromonas gingivalis, a periodontopathogen, is an oral anaerobic Cram-n egative bacterium with numerous fimbriae on the cell surface, Fimbriae have been considered to be an important virulence factor in this organism. We a nalyzed the genomic DNA of transposon-induced, fimbria-deficient mutants de rived from ATCC 33277 and found that seven independent mutants had transpos on insertions within the same restriction fragment. Cloning and sequencing of the disrupted region from one of the mutants revealed two adjacent open reading frames (ORFs) which seemed to encode a two-component signal transdu ction system. We also found that six of the mutants had insertions in a gen e, fimS, a homologue of the genes encoding sensor kinase, and that the inse rtion in the remaining one disrupted the gene immediately downstream, fimR, a homologue of the response regulator genes in other bacteria. These findi ngs suggest that this two-component regulatory system is involved in fimbri ation of P. gingivalis.