Contribution of Porphyromonas gingivalis 40-kDa Outer Membrane Protein to Coaggregation of P. gingivalis Vesicles with Streptococcus gordonii Cells.

Abstract

Porphyromonas, gingivalis, a pathogen in adult periodontitis, produces extracellular vesicles which cannot adhere to the tooth surface. In contrast, Streptococcus gordonii is one of the first oral bacteria to colonize on tooth surfaces and can be expected to support subsequent colonization by other bacteria. We previously reported the cloning of a 40-kDa outer membrane protein (40-kDa OMP) -coding gene from P. gingivalis 381 and that the protein was found to be localized in the vesicles. The aim of the present study was to clarify whether the 40-kDa OMP contributes to the coaggregation of P. gingivalis vesicles with S. gingivalis cells. A flocculation assay revealed that P. gingivalis vesicles and S. gingivalis cells were capable of coaggregation. Heat or protease treatments of P. gingivalis vesicles completely inhibited coaggregation activity, whereas these treatments on S. gingivalis cells only partially reduced coaggregation activity. The coaggregation of this pair was partially inhibited in the presence of an affinity-purified antibody against recombinant 40-kDa OMP or maltose, and was completely inhibited in the presence of both. These findings suggest that there are at least two kinds of adhesin for S. gingivalis in cells on the surface of P. gingivalis vesicles.