The CRISPR-cas repertoire of Kluyvera ascorbata: insights from genomic data.

The genus Kluyvera has gained increasing attention due to their emerging role as opportunistic pathogens and their antibiotic resistance determinants. Various approaches have been employed to reveal genomic insights into the evolution and pathogenicity of Kluyvera species. However, detailed knowledge about Kluyvera-specific clustered regularly interspaced short palindromic repeats (CRISPR) is still missing. In this study, a genome-mining approach was employed for the characterization of CRISPR-Cas loci in a total of 13 complete Kluyvera genomes using CRISPRCasFinder and related tools. Out of 13 species, only K. ascorbata displayed multiple CRISPR-Cas arrays and a complete set of cas genes characteristics of a type I-E system. Spacer analysis revealed potential targets within phage and plasmid sequences, indicating historical exposure to mobile genetic elements. Furthermore, a phylogenetic tree constructed using the Cas3 protein sequence positioned K. ascorbata closely with other enteric bacteria, including Salmonella spp. and Citrobacter spp. This study provides the first detailed insight into the CRISPR-Cas architecture of K. ascorbata. Although there is no significant diversity of the CRISPR-Cas system identified in this species, it can emphasize a role as active immune defenses against invaders and offer a foundation for future functional and evolutionary investigations. Moreover, difficulties in identification of the genus Kluyvera can be overcome through the CRISPR-Cas system using next-generation diagnostics tools.