Pyridoxal

Bacterial strains and culture condition G. adiacens ATCC 49175, A. defectiva ATCC 49176, and their two isolates, G. adiacens a-1 and a-2 and A. defectiva d-1 and d-2, were extracted from the dental plaque of healthy human volunteers and stored at -70° for use in this study (Tajika S, Dent J Iwate Med Uni, 21, [271] [272] [273] [274] [275] [276] [277] [278] [279] [280] [281] [282] [283] [284] [285] 1996) . To isolate G. adiacens and A. defectiva from dental plaque samples, colonies demonstrating bacteriolytic activity on Todd-Hewitt (Difco Laboratories, Detroit, MI, USA) agar plates containing heat-killed Micrococcus luteus cells were isolated after incubation at 37°C for 24 h from oral specimens. These isolates were then identified as G. adiacens or A. defectiva after performing biochemical tests and using the PCR-RFLP method [9] . Bacteria were cultured in Todd-Hewitt broth (THB; Difco Laboratories) supplemented with 10 µg/mL pyridoxal hydrochloride (Fujifilm Wako Pure Chemicals, Tokyo, Japan) and 200 µg/mL l-cysteine hydrochloride (Sigma-Aldrich, St. Louis, MO, USA) and were maintained at 37°C for 24 h. In other experiments, bacteria were cultured with 37 kBq of [methyl-3 H]-thymidine (PerkinElmer Japan, Yokohama, Japan) per mL of THB containing pyridoxal and l-cysteine for radioactive labeling.