design: Microbial genomic DNA was isolated from stool samples using the FastPure Stool DNA Isolation Kit (Magnetic bead) from MJYH, Shanghai, China, following the manufacturer's protocol. The region of V3 and V4 of the bacterial 16S rRNA genes were amplified using primer pairs 27F (5-AGRGTTYGATYMTGGCTCAG-3) and 1492R (5-RGYTACCTTGTTACGACTT-3) with an ABI GeneAmp 9700 PCR thermal cycler (ABI, CA, USA). The PCR amplification conditions included an initial denaturation at 95C for 3 minutes, followed by 27 cycles of denaturation at 95C for 30 seconds, annealing at 55C for 30 seconds, and extension at 72C for 45 seconds, with a final extension at 72C for 10 minutes, concluding at 10C. Each sample underwent triplicate amplification. Post-electrophoresis, PCR products were purified using AMPure PB beads (Pacific Biosciences, CA, USA) and quantified with Synergy HTX (Biotek, USA). The purified amplicons were pooled in equimolar ratios and subjected to paired-end sequencing on an Illumina MiSeq PE300 platform (Illumina, San Diego, USA) by Majorbio Bio-Pharm Technology Co. Ltd. (Shanghai, China), adhering to standard protocols.