H3-type VI secretion system modulates virulence factors by regulating signal molecules in Pseudomonas aeruginosa

Objectives: To characterize the regulatory and functional pathways of H3-type VI secretion system in Pseudomonas aeruginosa
Methods: Construction of deletion mutant of PAO1(ΔclpV3) and phenotypic assays
measurement of lux-based promoter activity assays
Galleria mellonella infection model
Results: Several virulence factors (pyocyanin production, motility activities, protease activity, and type III secretion system) were down-regulated in PAO1(ΔclpV3) in comparison with wild-type PAO1. Quantification of the second messenger cAMP and quorum sensing signal molecules showed that deactivation of H3-T6SS resulted in significantly lower level production of these signal molecules which can explain the down-regulated virulence factors. Studies using a Galleria mellonella infection model also indicated that H3-T6SS plays a significant role in bacteria pathogenicity in vivo.
Conclusions: H3-T6SS of P. aeruginosa, therefore, is an important system that help fight other bacteria for their ecological niche and are important in the pathogenicity process. It seems to be a potential therapeutic target against P. aeruginosa infection.