design: Sequencing was performed on an Illumina NovaSeq6000 Genome Sequencer (paired-end 250 bp) (Novogene Technology Co., Ltd., Tianjin, China). Paired- end reads were assigned to samples based on their unique barcode and truncated by cutting off the barcode and primer sequence. Paired-end reads were merged using FLASH (V1.2. 1 1, http://ccb.jhu.edu/software/FLASH/) (Magoc T et al.,2011), a very fast and accurate analysis tool, which was designed to merge paired- end reads when at least some of the reads overlap theread generated from the opposite end of the same DNA fragment, and the splicing sequences were called raw tags. Quality filtering on the raw tags were performed using the fastp (Version 0.23.1) software to obtain high-quality Clean Tags (Bokulich NA et al.,2012). The tags were compared with the reference database (Silva database (16S), https://www.arb-silva.de/) using UCHIME Algorithm (http://www.drive5.com/usearch/manual/uchime_algo.html) to detect chimera sequences, and then the chimera sequences were removed (Edgar RC et al.,2011). Then the effective tags were finally obtained. Sequences were binned into operational taxonomic units (ASVs) at a 100% similarity (RC 2013) using QIIME 2 (Bolyen et al., 2019).