S. mutans strain MT8148 (serotype c) was used in the present study [10 (link)]. Bacterial organisms were grown at 37°C in brain-heart infusion (BHI) medium or Todd-Hewitt (TH) medium, as well as on Mitis Salivarius agar, each obtained from Becton Dickinson and Co. (Franklin Lakes, NJ, USA). When spectinomycin- or erythromycin-resistant S. mutans strains were cultured, spectinomycin (1 mg/ml) or erythromycin (10 μg/ml) was supplemented as necessary.
Escherichia coli DH5α (Nippon Gene, Tokyo, Japan), used as the host strain for transformation of plasmid DNA, was cultured in Luria-Bertani (LB; 1% tryptone, 0.5% yeast extract, 0.5% NaCl) medium while LB agar plate was prepared by adding 1.5% agar. Ampicillin sodium (100a μg/ml) was added to the medium for subcloning using a pGEM-T Easy Vector (Promega Co., Madison, WI, USA), while erythromycin (500 μg/ml) was added for use of pVA838 [22 (link)]. All antibiotics were obtained from Wako Pure Chemical Industries (Osaka, Japan).
Escherichia coli DH5α (Nippon Gene, Tokyo, Japan), used as the host strain for transformation of plasmid DNA, was cultured in Luria-Bertani (LB; 1% tryptone, 0.5% yeast extract, 0.5% NaCl) medium while LB agar plate was prepared by adding 1.5% agar. Ampicillin sodium (100a μg/ml) was added to the medium for subcloning using a pGEM-T Easy Vector (Promega Co., Madison, WI, USA), while erythromycin (500 μg/ml) was added for use of pVA838 [22 (link)]. All antibiotics were obtained from Wako Pure Chemical Industries (Osaka, Japan).
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