Amplification of the rpoB Gene from Lactobacillus plantarum and Oenococcus oeni. Genomic DNA of L. plantarum and O. oeni was isolated from a single colony, with the Microbial DNA extraction kit (CABRU, Milan, Italy) according to manufacturerÕs procedure. For the PCR experiment, about 100 ng of genomic DNA was added to a 50-(L PCR mixture containing 1.25 U of Taq polymerase (Qiagen, Milan, Italy) 0.2 mM of each dATP, dTTP, dGTP, dCTP, 10 mM Tris-HCl pH
8.3, 50 mM KCl, 1.5 mM MgCl 2 , and 0.4 mM of primers rpoB1 (ATTGACCACTTGGGTAACCGTCG), rpoB1O (ATCGATCACTTAGGCAATCGTCG), and rpoB2 (CGCCCGCCGCGCGCGGCGGGCGGGGCGGGGGCACGGGGGGGCACGATCACGGGTCAAACCACC) [19, 20]. Primer rpoB2 has a GC-rich clamped DNA sequence in order to avoid duplex DNA problems and to improve detection of
single-base changes [21]. The reaction mix was cycled through the following temperature profile: 94°C 5 min; 94°C 1 min; 58°C 1 min; 72°C 1 min for the first 15 cycles, then 15 cycles at 52°C as annealing temperature. The PCR reaction was terminated at 72°C for 10 min and thereafter cooled to 4°C.