Identification of a specific domain of <italic>Porphyromonas gingivalis</italic> Hgp44 responsible for adhesion to <italic>Treponema denticola</italic>.

Interaction between two periodontal pathogens, <italic>Porphyromonas gingivalis</italic> and <italic>Treponema denticola</italic>, contributes to plaque biofilm formation. <italic>Porphyromonas gingivalis</italic> forms aggregates with <italic>T. denticola</italic> through its adhesion/hemagglutinin domain (Hgp44). In this study, we investigated the specific domain of <italic>P. gingivalis</italic> Hgp44 responsible for adhesion to <italic>T. denticola</italic> using expression vectors harboring <italic>P. gingivalis</italic> Hgp44 DNA sequences encoding amino acid residues 1–419. Six plasmids harboring fragments in this region were generated by PCR amplification and self-ligation, and recombinant proteins r-Hgp44 (residues 1–419), r-Hgp441 (residues 1–124), r-Hgp442 (1–199), r-Hgp443 (1–316), r-Hgp444 (199–419), r-Hgp445 (124–198) and r-Hgp446 (199–316) were produced, as confirmed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and immunoblotting. r-Hgp44, r-Hgp443 and r-Hgp446 showed greater adhesion to <italic>T. denticola</italic> sonicates than the control, as determined by enzyme-linked immunosorbent assay. r-Hgp446 reduced the coaggregation of <italic>P. gingivalis</italic> and <italic>T. denticola</italic>. Scanning electron and confocal laser scanning microscopy analyses revealed that r-Hgp446 reduced dual-species biofilm formation. Our results indicate that residues 199–316 of <italic>P. gingivalis</italic> Hgp44 are mainly responsible for adhesion to <italic>T. denticola</italic>; inhibiting this domain could potentially disrupt periodontopathic biofilm formation and maturation. <italic>Porphyromonas gingivalis</italic> Hgp44 residues 199–316 are responsible for adhesion to <italic>Treponema denticola</italic>; inhibition of this domain may disrupt periodontopathic biofilm formation and maturation. [ABSTRACT FROM AUTHOR]