2.9. 16S rRNA Sequence Preprocessing
The sequencing was carried out using Illumina paired-end technology, specifically targeting the V3–V4 region of the 16S rRNA gene. To assess the quality of the raw sequencing data, a thorough initial quality screening was conducted using FastQC (version 0.12.1) and MultiQC (version 1.12) tools. Subsequently, all data preprocessing was executed using the QIIME 2 software [