Porphyromonas gulae Strains and Gingival Epithelial Cells

P. gulae strains ATCC 51700 (fimA type A), D040 (fimA type B), and D049 (fimA type C) were selected from the stock culture collection in our laboratory^{7 (link),8 (link),24 (link)}. Bacterial cells were grown anaerobically at 37 °C for 24 h in trypticase soy broth supplemented with yeast extract (1 mg/ml), haemin (5 μg/ml), and menadione (1 μg/ml), as previously described^{48 (link)}; they were then used in the following experiments. Ca9-22 cells (originally isolated from human gingival epithelia) were obtained from the Japanese Collection of Research Bioresources (Tokyo, Japan); these cells were used as an in vitro counterpart of gingival epithelial cells^{28 (link)} because they have been widely used as an in vitro culture model of gingival epithelial cells^{28 (link),49 (link)}. The cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Wako, Osaka, Japan) supplemented with 10% fetal bovine serum at 37 °C in 5% CO₂.