Regulation of the Porphyromonas gingivalis fimA (fimbrillin) gene

In common with many bacterial virulence genes, the fimbrillin (fimA) gene o f Porphyromonas gingivalis is modulated in response to environmental fluctu ation. The trans-acting components that comprise the regulatory system for transcriptional activity of the fimA gene in P. gingivalis were investigate d. Three major proteins were found to bind to the upstream region of the fi mA promoter. One of these proteins was fimbrillin itself, and the other two were a major arginine protease (Rgp) and lysine protease (Kgp). Production of these proteins was necessary for maximal fimA transcription. An exogeno us fimA promoter-lacZ reporter was inactive when introduced into a strain o f P. gingivalis carrying a mutation in the indigenous fimA gene. Furthermor e, fimA mRNA levels were significantly decreased in rgp and kgp mutant stra ins. These data indicate that P. gingivalis has evolved multiple levels of control of fimbrial gene expression to enhance its survival in hostile envi ronments.