Clustered Regularly Interspaced Short Palindromic Repeats-Cas system regulatesSalmonellavirulence

Abstract

AbstractObjectivesInvestigating the type 1-E CRISPR-Cas-mediated regulation ofSalmonellapathogenesis.MethodsWe assessed the pathogenicity of the wild-type and CRISPR-Cas knockout strains using infection models. The mechanisms were elucidated using antimicrobial assays and expression analysis.ResultsCRISPR-Cas knockout strains were defective in invasion and proliferation in intestinal epithelial cells and macrophages. However, proliferation defects were not observed in the Gp91phox-/-macrophages, suggesting the system’s role in antioxidant defence. The knockout strains show hampered colonization inin-vivoinfection models, possibly due to increased sensitivity against innate immune barriers like antimicrobial peptides, complement proteins and oxidative stress. The expression studies of various virulence regulators:pmrgenes, anti-oxidant genes, SPI-1 and SPI-2 encoded master regulators, and effectors showed repressed expression in the knockout strains. Some of these genes could be directly regulated by the CRISPR-spacers owing to partial complementarity between the sequences.ConclusionOverall, our study shows that the CRISPR-Cas system positively regulatesSalmonellapathogenesis by regulating the expression of different virulence factors.