design: Library preparation for 16S rRNA gene sequencing was performed according to the recommended protocols established by Illumina. V3V4 hypervariable regions of the bacterial 16S rRNA gene were amplified using the primers 341F and 805R. Dual indices and Illumina sequencing adapters were attached using the Illumina Nextera XT Index kit. Sequencing was done with the Illumina MiSeq system using a MiSeq reagent kit v3 (2  300 cycles).