design: Using the extracted stool DNA as a template, the V3/V4 region of the 16S rRNA gene was amplified by PCR. The amplified PCR products were purified with VAHTS DNA Clean Beads (Vazyme). A sequencing library was then prepared, and paired-end sequencing (2  300 bp) was performed using the MiSeq System and the MiSeq Reagent Kit v3 (Illumina).