[Influence of Polystyrene Microplastics on the Formation and Structural Change of <i>Pseudomonas aeruginosa</i> Biofilm].

Microplastic pollution in the water environment is becoming increasingly serious, impacting the growth and development of aquatic organisms. There are limited studies on the mechanisms of microplastic effects on biofilm formation. Therefore, in this study, the effects of polystyrene microplastics (PS-MPs) were investigated on the biofilm formation and development of <i>Pseudomonas aeruginosa</i>. Different concentrations and particle sizes of PS-MPs were selected for exposure tests to explore the effects on biofilm biomass, oxidative stress levels, biofilm structure, and population sensing system. The results showed that PS-MPs induced severe oxidative stress and inhibited biofilm formation and development, and the smaller the particle size, the stronger the inhibitory effect was. The inhibition effect was 0.1 μm>0.5 μm≈1 μm>5 μm. PS-MPs caused severe physical damage through contact with bacteria. The thickness of the biofilm was significantly reduced, damaging the structural stability. The bacteria in the biofilm secreted extracellular polymers to resist the stress of PS-MPs. Meanwhile, PS-MPs interfered with the QS system of <i>P. aeruginosa</i>; down-regulated the expression levels of key genes <i>lasI, lasR, rhlI</i>, and <i>rhlR</i>; inhibited the synthesis and secretion of signal molecules and related virulence factors; and ultimately affected the formation and structural stability of biofilms.