16S rRNA gene sequencing
The Illumina MiSeq DNA Amplicon sequencing library was achieved by polymerase chain reaction (PCR) using Fluidigm chemistry (Fluidigm Corporation, South San Francisco, CA, USA) and PCR protocol. To amplify the V4 target region of the 16S rRNA, the primers 515F (5' - GTG CCA GCM GCC GCG GTA A  3) and 806R (5'- GGA CTA CHV GGG TWT CTA AT) were used (Caporaso et al., 2011). These primers were adapted to the Fluidigm system and equipped with a tail that is complementary to parts of the Illumina sequencing adapters resulting in 515F-CS1 and 806R-CS2. All PCRs were performed with a total volume of 20 l containing 3 l H2O, 10 l AmpliTaq Gold 360 Master Mix, 2 l TS primer mix (= 96 l H2O, 2 l primer 515F- CS1 and 2 l primer 806R- CS2), 3 l of barcode-containing sequencing adapter and 2 l DNA sample.