2.6.3. TTGE analysis
PCR products obtained from the V3 region amplification as described above were subjected to TTGE analysis. TTGE was performed by using the Dcode universal mutation detection system (Bio-Rad). Polyacrylamide (8%) gels were prepared and run with 1× TAE buffer (40 mM Tris base, 20 mM glacial acetic acid, 1 mM EDTA, pH 8.3) diluted from 50× TAE buffer. Gels were prepared with 8% (wt/vol) acrylamide stock solutions (acrylamide-bisacrylamide, 37.5:1) and a final urea concentration of 7 M. The final electrophoresis conditions were 70 V for 16 h with an initial temperature of 63 °C and a final temperature of 70 °C (the temperature was increased 0.4 °C per h). Samples (20 μl) of PCR products were deposited in wells. A magnetic stirrer was used to mix the buffers and improve the temperature gradient homogeneity. After runs, gels were stained for 30 min with ethidium bromide (0.5 μg/ml of 1× TAE buffer), rinsed for 20 min in 1× TAE buffer, and photographed on a UV transillumination table.
3. Results and discussion