Yt broth

Streptococcus mutans XC (Koga et al., 1989 (link)) and its derivatives (Table 1) were anaerobically grown in Brain Heart Infusion broth (BHI; Becton Dickinson, Franklin Lakes, NJ, United States) at 37°C. Where necessary, erythromycin, kanamycin, or 4-chloro-phenylalanine (p-Cl-Phe; Sigma-Aldrich Japan, Tokyo, Japan) was added to a final concentration of 20 μg ml^-1, 700 μg ml^-1, or 200 μg ml^-1, respectively. E. coli strains DH5α (Thermo Scientific Japan, Tokyo, Japan) and BL21 (Promega, Tokyo, Japan) were used for DNA manipulation and recombinant protein purification, respectively, and were grown aerobically in 2 × YT broth (Becton Dickinson) at 37°C. Where required, chloramphenicol, erythromycin, ampicillin, and kanamycin were added to the media to final concentrations of 20 μg ml^-1, 200 μg ml^-1, 100 μg ml^-1, and 70 μg ml^-1, respectively.

The following bacterial strains were used in this study: Streptococcus mutans UA159, Streptococcus sobrinus OMZ175, Streptococcus mitis ATCC 49456, Streptococcus oralis ATCC 10557, Streptococcus gordonii ATCC 10558, Streptococcus sanguinis SK36, Streptococcus parasanguinis ATCC 15912, Streptococcus tigurinus ATCC 15914, Streptococcus australis ATCC 700641, Streptococcus infantis ATCC 700779, Streptococcus salivarius HHT, Streptococcus anginosus NCTC 10707, Streptococcus intermedius ATCC 27335, and Escherichia coli DH5α
E. coli strains were grown in 2×YT Broth (Becton Dickinson, Franklin Lakes, NJ, USA). Oral streptococci strains were grown in brain heart infusion (BHI) broth (Becton Dickinson) at 37°C in 5% CO₂. Antibiotics were used at the following concentrations: 300 μg/mL erythromycin and 50 μg/mL ampicillin for E. coli, 20 μg/mL erythromycin for oral streptococci, 600 μg/mL spectinomycin for S. mutans and S. anginosus, and 150 μg/mL spectinomycin for S. sanguinis.