FIG. 7.

Model for fimA expression. (A) fimA expression is upregulated, which may be mediated through a two-component system. Expression of pg2167 is repressed without CC5A signal. (B) P. gingivalis interacts with an S. cristatus surface protein via an unknown receptor. Subsequent signal transduction induces pg2167 expression, and the latter may prevent fimA transcription and promote pg2131 transcription. The production of fimbrillin is decreased as a result of transcriptional downregulation of fimA, even though pg2131 is upregulated by pg2167. Reduced production of fimbrillin further reduces fimA transcription through negative feedback.