design: The 16S rDNA was amplified using V3 forward primer (5-TCG TCG GCA GCG TCA GAT GTG TAT AAG AGA CAG CCT ACG GGN GGC WGC AG-3) and V4 reverse primer (5-GTC TCG TGG GCT CGG AGA TGT GTA TAA GAG ACA GGA CTA CHV GGG TAT CTA ATC C-3). Index PCR with sequencing adapters attached to amplified DNA was performed using a Nextera XT Index kit (Illumina, San Diego, CA, USA). After quantifying, normalizing, and pooling the libraries, each amplicon was sequenced using a MiSeq instrument (Illumina, San Diego, CA, USA)