Cas9 modulates Campylobacter jejuni virulence traits inside intestinal epithelial cells

The CRISPR-associated protein 9 (Cas9) produced by disease-associated strains of <i>Campylobacter jejuni</i> contributes to full virulence, including immune evasion and bacterial survival inside eukaryotic cells. In this work, we explored the role of <i>C. jejuni</i> Cas9 (CjeCas9) in cell envelope integrity, antibiotic resistance, intracellular survival inside Caco-2 intestinal epithelial cells and Toll-like receptor 2 (TLR-2) activation. We show that CjeCas9 modulates the permeability of the <i>C. jejuni</i> cell envelope, sialylated lipooligosaccharide expression and susceptibility to ciprofloxacin, the most commonly prescribed antibiotic to treat <i>C. jejuni</i> infections. Moreover, we reveal that WT production of CjeCas9 increased intracellular survival of <i>C. jejuni</i> inside Caco-2 intestinal epithelial cells by a factor of 550 compared to the respective <i>cas9</i> gene deletion mutant and that intracellular survival was associated with the activation of TLR-2. In conclusion, we established that CjeCas9 modulates <i>C. jejuni</i> (intracellular) virulence traits, including intracellular survival.