Bead beading isolation was done to extract genomic DNA using the QIAamp DNA Kit (QIAGEN, Hilden, Germany), following the manufacturer's protocol. The extracted DNA concentration was measured by Qubit 2.0 Fluorometer (Life Technology, Carlsbad, CA). DNA quality was detected by 1.0% agarose gel electrophoresis. Then, the 16S rDNA gene regions (V3 and V4) were amplified by PCR. The 16S rDNA libraries were sequenced on the Illumina MiSeq platform PE300 mode (Illumina, USA)