DGGE was performed using a D-Code System maintained at a constant temperature of 60 C in 1TAE buffer. PCR products were loaded onto 8% (w/v) polyacrylamide gels (37.5:1, acrylamide/bisacrylamide) using a denaturing gradient ranging from 35% to 65% denaturant (100% denaturant corresponded to 7 mol urea and 40% formamide in the 1TAE buffer). Gels were run at 80 V for 12 h and stained with SYBR Gold nucleic acid stain (Invitrogen, Carlsbad, CA). The resultant image was analysed using Quantity One 4.6.2 software (Bio-Rad, Hercules, USA) to obtain the fingerprint patterns and to calculate the band similarities