We adjusted each of the washed P. gingivalis suspensions to an optical density of 550 nm (OD550; 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0) and then placed 150 μL per well into a 96-well plate. We measured the fluorescence of each well with infiniteM200 (Tecan Group Ltd., Männedorf, Switzerland) connected to PLATEmanagerV5 (Wako Pure Chemical Industries, Ltd, Osaka, Japan). The optimal excitation wavelength for detection was 460 nm and the emission wavelength was 703 nm.