Genome mining approach reveals the CRISPR-Cas systems features and characteristics in Lactobacillus delbrueckii strains

This study employed a comprehensive genome-mining approach to characterize CRISPR-Cas systems in <i>Lactobacillus delbrueckii</i> strains. The analysis involved retrieving 105 genome sequences to explore the variety, occurrence, and evolution of CRISPR-Cas systems within the species. Homology analysis of spacer sequences in detected CRISPR arrays was conducted to assess the variety of target phages and plasmids. The evolutionary trajectories of spaceromes in each subtype of CRISPR arrays were determined by analyzing acquisition and deletion events under the selection pressure of foreign plasmids and phages. Among the analyzed strains, 53 contained only one CRISPR-Cas locus, 11 had two loci, and 21 featured three loci with complete CRISPR-Cas systems. Subtype designation of the results of current study revealed that 56 % of these systems belong to subtypes I-E/I-C, 23 % to subtypes III-A/III-D, and 17 % to subtype II-A. Notably, certain plasmids were found to be specifically targeted by distinct CRISPR array systems. The comparison of spacer sequences with phage genomes indicated that strains containing only CRISPR-Cas type-I systems targeted a broader range of phages. In conclusion, this study highlights the diversity of the three identified CRISPR-Cas types in <i>L. delbrueckii</i> strains and emphasizes their significant role in defense against phage invasion.