ThePseudomonas aeruginosaaccessory genome elements influence virulence towardsCaenorhabditis elegans

ABSTRACT Multicellular animals and bacteria frequently engage in predator-prey and host-pathogen interactions, such as the well-studied relationship between Pseudomonas aeruginosa and the nematode Caenorhabditis elegans . This study investigates the genomic and genetic basis of bacterial-driven variability in P. aeruginosa virulence towards C. elegans . Natural isolates of P. aeruginosa that exhibit diverse genomes display a broad range of virulence towards C. elegans . Using gene association and genetic analysis, we identified accessory genome elements that correlate with virulence, including both known and novel virulence determinants. Among the novel genes, we found a viral-like mobile element, the teg block, that impairs virulence and whose acquisition is restricted by CRISPR-Cas systems. Further genetic and genomic evidence suggests that spacer-targeted elements preferentially associate with lower virulence and suggest a positive, albeit indirect, role for host CRISPR-Cas systems in the restriction of accessory genome elements that may be detrimental to virulence.