ABSTRACT Coinfection of Pseudomonas aeruginosa ( P. aeruginosa ) and Staphylococcus aureus ( S. aureus ) is frequently observed. Our previous study demonstrated that S. aureus ‐derived extracellular vesicles (SaEVs) promote P. aeruginosa pathogenicity by increasing lipopolysaccharide (LPS) production, promoting biofilm formation and decreasing the uptake of P. aeruginosa by macrophages. Proteomic analysis revealed that SaEVs enhance the production of PslE, an exopolysaccharide biosynthetic protein in P. aeruginosa , but the role of Psl exopolysaccharide polymerization on SaEV‐mediated P. aeruginosa pathogenicity is unclear. In this study, a pslE ‐deletion mutant of P. aeruginosa (PaΔ pslE ) was constructed, and the effect of SaEVs on the pathogenicity of this mutant was evaluated. Our results showed that SaEVs significantly increased the expression of pslA , E , J , K , and L genes in the psl cluster of P. aeruginosa wildtype (PaWT), and this effect was abolished in PaΔ pslE . In addition, LPS production and biofilm formation were reduced in PaΔ pslE compared to PaWT. SaEVs significantly enhanced LPS production and biofilm formation in PaWT. On the other hand, the effects of SaEVs on the production of lipid A and LPS core and biofilm formation in PaΔ pslE were abolished. Invasion of PaWT and PaΔ pslE into HaCaT human epithelial cells was not significantly different and the effect of SaEVs on these bacterial cell invasions was not found. However, the uptake of SaEV‐treated PaWT by macrophages significantly reduced compared to nontreated PaWT, whereas SaEVs did not alter the uptake of PaΔ pslE . These results suggest that PslE is required for SaEV‐mediated P. aeruginosa pathogenicity. SaEVs upregulate pslE gene as well as other exopolysaccharide polymerization‐related genes, increase LPS production and biofilm formation, and affect the uptake of P. aeruginosa by macrophages.
Subsomwong et al. (2026) studied this question.