CRISPR-Cas in Campylobacter jejuni controls membrane integrity and pathogenicity

The bacterial cell envelope is the most important structure to counteract the early stages of (a)biotic stress. In Campylobacter jejuni, a zoonotic human intestinal pathogen, modification of the bacterial cell envelope and Clusters of Regularly Interspaced Short Palindromic Repeats and associated genes (CRISPR-Cas) have both been linked to defense and virulence features. Current evidence suggests that a dual function exists between the CRISPR-Cas system in C. jejuni and the regulation of cell envelope exposed outer surface structures. The objective of this study is to elucidate how the CRISPR-Cas system in C. jejuni modulates cell envelope exposed outer surface structures during (a)biotic stressors. Here, we show that loss of cell envelope structures or the CRISPR- Cas marker gene cas9 significantly alters membrane permeability, antibiotic resistance, swarming behavior and immune recognition. Bioinformatics and RNA analysis reveal a potential mechanism showing that Cas9 and CRISPR RNAs control the expression of cell envelope structures, as evidenced in other microorganisms. This study indicates that the CRISPR-Cas system in C. jejuni is actively involved in the regulation of cell envelope exposed outer surface structures affecting antibiotic resistance, virulence features and immune recognition. C. jejuni could utilize its CRISPR-Cas system to regulate its cell envelope structures in order to survive encountered (a)biotic stress in the environment or inside a host during infection. Currently, experiments are ongoing to unravel the exact regulatory mechanism.