2.4. 16S rDNA gene amplification and pyrosequencing
The primers 515F (50-GTGCCAGCMGCCGCGG-30) and 907R (50-
CCGTCAATTCMTTTRAGTTT-30) with a unique 6 bp tag sequence at
the 50-end of each were used to amplify theV4-V5 hypervariable
regions of the 16S rDNA gene (Xiong et al., 2012). The PCR reaction
mixture (25 mL) contained 1 mL of the purified template DNA,
2.5 mL of 10
PCR Mg2+ free buffer, 2.0 mL of 25 mM dNTP, 2.5 mL of
2.5 mM Mg2+, 0.5 mL (10 mM) of each primer, and 0.5 mL (1.25 U) of
Taq polymerase, which were then maintained by sterilized
ultrapure water. The thermal cycling conditions were as follows:
an initial denaturation at 94 C for 5 min; 15 cycles of 94 C for 60 s,
54 C for 30 s, and 72 C for 90 s; and a
final extension step at 72 C
for 10 min.