2.2 | CRISPR/Cas identification
Based on the feature of repeat sequences within one single CRISPR locus, CRISPRCasFinder web server (https://crispr.i2bc.paris-saclay.fr/Server/) divided CRISPR loci into ”confirmed” and ”questionable” CRISPR. In all strains containing confirmed CRISPR loci, 10000 bp upstream and downstream of the loci were extracted. These sequences were then uploaded to the CRISPRCasFinder web server to determine the presence and content of cas genes. The subtypes of all CRISPR/Cas system were determined by the CRISPRCas typer server (https://typer.crispr.dk/#/submit ) with default parameters [30]. Type I-E and type I-E* systems were classified based on the content of cas genes, as previously described [31].