PerkineElmer Applied Biosystems, Carlsbad, CA, USA) using the prokaryotic 16S rRNA universal primers: pA (50-AGAGTTTGATCCTGGCTCAG-30) and pH (50-AAGGAGGTGATCCAGCCGCA-30) under the following conditions: one cycle at 95C for 5 min; 30 cycles at 94C for 50 s, 60C for 50 s, 72C for 90 s; and one cycle at 72C for 7 min.