library_construction_protocol: Genomic DNA was extracted and the quality evaluation was performed by agarose gel electrophoresis. The V3 V4 region of the 16S rRNA gene was amplified by PCR using a forward primer 338F and a reverse primer 807R. Then the PCR products were recovered and purified. The purified PCR products were library-constructed. submitted_instrument_model: Illumina NextSeq 2000