design: Total genomic DNA from samples was extracted according to the descriptions.16S rRNA genes were amplified using the specific primer with a 12-nt unique barcode. The PCR mixture (50 l) contained 2 PCR buffer, 1.5 mM MgCl2, 0.4 M each dNTP, 1.0 M each primer, 0.5 U of KOD-Plus-Neo (TOYOBO), and 10 ng template DNA.Samples with a bright major band between 200400 bp were selected for further experiments. An Illumina TruSeq DNA PCR-Free Sample Prep Kit (FC-121-3001/3003) was used for library construction and index codes were added. The resulting library was subjected to paired-end sequencing (2250 bp) with an Illumina Hiseq Rapid SBS Kit v2 (FC-402-4023 500 Cycle).