Proteomics and functional analysis of outer membrane vesicle from Pseudomonas aeruginosa under SOS

The bacterial SOS response and outer membrane vesicle (OMV) production are conserved among Gram-negative bacteria, both contributing to virulence and biofilm development. SOS may link to OMV generation. To investigate such a connection, we conducted functional and proteomic analyses of OMVs from Pseudomonas aeruginosa. Functionally, OMVs mediated macrophage cytotoxicity and contributed to biofilm formation. OMV production and the cytotoxicity increased when the OMV-producing cells were SOS-induced by ciprofloxacin treatment, but decreased when LexA repressed SOS. Proteomic analysis revealed that proteins whose genes are known to be expressed during SOS were found predominantly in OMV proteins (OMVps) produced by the SOS-induced cells. These OMVps thus is termed SOS-OMVps. Many cytotoxic and biofilm-related proteins were also found in SOS-OMVps while some in the SOS-independent OMVps. Therefore, SOS appears to play a role in the antibiotic-stimulated OMV production, which contributes to cytotoxicity and biofilm formation.