D1709 (CRX2211246)
DNA for each sample was extracted with QIAamp Fast DNA Stool Mini Kit (Qiagen, Hilden, Germany).  then V3-V4 of 16S rDNA was amplified by two-step PCR. Finally, the amplicons were sequenced on Illumina HiSeq 2500 platform in pair-end 300 bp mode.