Identification of a molecule of Porphyromonas gingivalis that binds to Streptococcus gordonii.

The molecules that mediate the adherence of Porphyromonas gingivalis, a periodontal pathogen, to Streptococcus gordonii, a commensal plaque organism, were investigated. Outer membrane proteins of P. gingivalis were labelled with biotin, extracted by EDTA and reacted with S. gordonii cells. Interactive porphyromonas components were identified by SDS-PAGE of the S. gordonii cells followed by electroblotting and visualization of the adsorbed porphyromonas molecules with streptavidin-alkaline phosphatase. A P. gingivalis molecule of 35 kDa bound to S. gordonii. Monospecific polyclonal antibodies to the 35 kDa protein inhibited binding of P. gingivalis to S. gordonii by 71%. The antibodies also reacted with the P. gingivalis fimbriae, indicating that the 35 kDa molecule is antigenically related to, or associated with, the fimbriae.