design: Stool microbiome DNA was extracted according to the instructions of the Omega Stool DNA Kit (MoBio Laboratories, Carlsbad, CA). The extracted DNA was tested for DNA quality and concentration by 1% agarose gel electrophoresis and spectrophotometry. The quality-checked samples were stored at -20C for subsequent experiments. V3-V4 regions of the 64S rRNA gene were amplified and then sequenced using the Illumina MiSeq sequencing platform (Illumina, San Diego, CA) at Beijing Ovison Gene Technology Co. Raw data was filtered to remove adapter sequences and low-quality reads.