Human gastric microbiota
The samples were processed for amplicon sequencing targeting the 16S rRNA gene. DNA was extracted from gastric samples using the CTAB/SDS method. Specific primers (515F-806R) were used for amplification of the 16S V3-4 region. PCR products were purified and indexed for sequencing. Libraries were prepared using the TruSeq DNA PCR-Free Sample Preparation Kit and sequenced on an Illumina NovaSeq 6000 platform using a paired-end approach (388 bp).