library_construction_protocol: DNA for each sample was extracted with TIANamp Stool DNA Kit. After quality access and concentration measurement, one step PCR was used to prepare the PCR Illumina sequencing libraries in a 25 uL reaction. The cDNA was purified by the addition of Clean Beads and then sequenced on an Illumina HiSeq2500 platform, which generated approximately 4.5 million reads of 16S rRNA V3 V4 amplicons.