Porphyromonas gingivalis cells coaggregated with Prevotella intermedia cell
s. The coaggregation was inhibited with L-arginine, L-lysine, N alpha -p-to
syl-L-lysine chloromethyl ketone, trypsin inhibitor, and leupeptin. Heat- a
nd proteinase K-treated P. gingivalis cells showed no coaggregation with P.
intermedia cells, whereas heat and proteinase K treatments of P intermedia
cells did not affect the coaggregation. The vesicles from P. gingivalis cu
lture supernatant aggregated with P intermedia cells, and this aggregation
was also inhibited by addition of L-arginine or L-lysine and by heat treatm
ent of the vesicles. The rgpA rgpB, rgpA kgp, rgpA rgpB kgp, and rgpA kgp h
agA mutants of P. gingivalis did not coaggregate with P. intermedia. On the
other hand, the fimA mutant lacking the FimA fimbriae showed coaggregation
with P intermedia as well as the wild type parent. These results strongly
imply that a heat-labile and proteinous factor on the cell surface of P. gi
ngivalis, most likely the gingipain-adhesin complex, is involved in coaggre
gation of P. gingivalis and P. intermedia.