Comparative genomics reveals the diversity of CRISPR–Cas locus in Azotobacter organisms.

This article focuses on the bioinformatic analysis of the CRISPR–Cas adaptive immune system in nitrogen-fixing Azotobacter species, which are important plant growth-promoting bacteria. The study identifies diverse CRISPR loci and Cas proteins in Azotobacter vinelandii and Azotobacter chroococcum strains, revealing a correlation between the structural stability of CRISPR repeat RNA hairpin loops and the number of spacers acquired, suggesting enhanced adaptive immunity. Phylogenetic analyses indicate evolutionary diversity and possible horizontal gene transfer of Cas elements within these species. The findings highlight the potential of these indigenous CRISPR–Cas systems to contribute to bacterial survival against bacteriophages and plasmids, supporting the use of Azotobacter strains as biofertilizers and providing a foundation for future research on their role in gene regulation and environmental adaptation.