For bacterial microbiome analyses, samples (n = 7 per experimental group) were used for 16S rRNA V3V4 amplicon library preparation. In summary, the V3V4 hypervariable region of the 16S rRNA gene (~460 bp) was amplified using universal bacterial primers (forward: 5-CCTACGGGNGGCWGCAG-3; reverse: 5-GACTACHVGGGTATCTAATCC-3). The resulting PCR products were purified with AMPure XP magnetic beads (Beckman Coulter, Brea, CA, USA) prior to library construction using the Nextera XT Index Kit (Illumina, San Diego, CA, USA). Sequencing was performed on an Illumina MiSeq platform using paired-end chemistry (2  300 bp) at Macrogen Inc. (Seoul, Republic of Korea).