Effects of low-level engineered nanoparticles on the quorum sensing of Pseudomonas aeruginosa PAO1.

The toxicity of engineered nanoparticles (ENPs) on bacteria has aroused much interest. However, few studies have focused on the effects of low-level ENPs on bacterial group behaviors that are regulated by quorum sensing (QS). Herein, we investigated the effects of nine ENPs (Ag, Fe, ZnO, TiO2, SiO2, Fe2O3, single-wall carbon nanotubes (SWCNTs), graphene oxide (GO), and C60) on QS in Pseudomonas aeruginosa PAOl. An ENP concentration of 100 μg L-1 did not impair bacterial growth. However, concentrations of 100 μg L-1 of Ag and GO ENPs induced significant increases in 3OC12-HSL in the culture and significantly promoted protease production and biofilm formation of PAO1. C4-HSL synthase and its transcription factors were less sensitive to 100 μg L-1 Ag and GO ENPs compared with 3OC12-HSL. Fe ENPs induced a significant increase in the 3OC12-HSL concentration, similar to Ag and GO ENPs. However, Fe ENPs did not induce any significant increase in protease production or biofilm formation. Different size distributions, chemical compositions, and aggregation states of the ENPs had different effects on bacterial QS. These whole circuit indicators could clarify the effects of ENPs on bacterial QS. This study furthers our understanding of the effects of low-level ENPs on bacterial social behaviors.