AHL-mediated quorum sensing drives plastisphere formation and elevates pathogenic potential

The biofilm colonizing plastic debris, termed "the plastisphere," is of growing global concern due to escalating plastic pollution. However, the biological mechanisms underpinning plastisphere formation remain poorly understood. Here, we analyzed public global metagenomes, revealing a significant enrichment of genes associated with quorum sensing (QS) and biofilm formation, with a pronounced signal for acyl-homoserine lactone (AHL) QS. Using controlled microfluidic and tubular column experiments, we further demonstrate that exogenous AHL actively promotes plastisphere formation, biomass accumulation, and extracellular polymeric substance production on microplastics, whereas a quorum-quenching agent (AHL acylase) effectively inhibits these processes. Multi-omics analyses revealed that AHLs can transcriptionally activate genes involved in adhesion, motility, chemotaxis, and matrix production, fundamentally reshaping community structure, restructuring inferred microbial interaction networks, and driving community assembly toward stronger deterministic selection. AHL stimulation also increased the relative abundance and expression of pathogen-associated and virulence-related functions, suggesting an elevated virulence potential within the plastisphere under QS-promoting conditions. Together, our findings establish AHL-mediated QS as a central driver of plastisphere assembly and a key determinant of risk profile, highlighting its critical role in understanding and potentially mitigating the growing environmental and health hazards associated with microplastic pollution.