Intergeneric communication in dental plaque biofilms

Dental plaque is a complex biofilm that accretes in a series of discrete st eps proceeding from a gram-positive streptococcus-rich biofilm to a structu re rich in gram-negative anaerobes. This study investigated information flo w between two unrelated plaque bacteria, Streptococcus cristatus and Porphy romonas gingivalis. A surface protein of S. cristatus caused repression of the P. gingivalis fimbrial gene (fimA), as determined by a chromosomal fimA promoter-lacZ reporter construct and by reverse transcription-PCR Signalin g activity was associated with a 59-kDa surface protein of S. cristatus and showed specificity for the fimA gene. Furthermore, P. gingivalis was unabl e to form biofilm microcolonies with S. cristatus. Thus, S. cristatus is ca pable of modulating virulence gene expression in P. gingivalis, consequentl y influencing the development of pathogenic plaque.