design: The initial DNA concentration was 10 ng per sample, the final PCR mix contained 25 ul LongAmp Hot Start Taq 2x Master Mix, 10 ul input DNA, 10 ul 16S barcode primers (each) and 5 ul nuclease free water. The reaction was performed using a thermal cycler (Biometra TAdvanced, Analytik Jena, Jena, Germany) with the following PCR conditions: initial denaturation at 95C for 1 min, 25 cycles of 95C for 20 s, 55C for 30 s, 65C for 2 min, followed by a final extension step at 65C for 5 min. The amplicons were purified with AMPure XP beads (Beckman Coulter, Brea, CA, USA) and eluted in 10 mM Tris-HCl pH 8.0 with 50 mM NaCl.