Nanoplastics shift arbuscular mycorrhizal fungal mediation of bacterial community assembly from diversity to compositional stability under arsenic stress.

Arbuscular mycorrhizal fungi (AMF) play a vital role in contaminated soil remediation, yet how NPs regulate AMF mediated arsenic (As) remediation under NP and As co-contamination remains unclear. This study aims to elucidate the effects of NP on the strategic shifts in AMF in response to As exposure. This study demonstrates that NP fundamentally redirect the strategy of AMF. The result shows that AMF inoculation significantly increased community diversity under individual NP or As stress. Instead, AMF orchestrated a profound restructuring of the microbial community, notably enriching key phyla such as Proteobacteria and Bdellovibrionota, and simplifying the co-occurrence network (reduced nodes, edges, and average degree) under the co-contaminated NP and As. Crucially, this community restructuring was not a degradation but a strategic optimization. AMF significantly enhances community compositional stability (manifested as reduced vulnerability and average avriation degree, and in-creased niche width) as well as soil ecosystem multifunctionality. Partial least squares path modeling (PLS-PM) confirmed that under AMF mediation, microbial community directly governed this enhanced compositional stability. Overall, NPs shift the primary ecological function of AMF from promoting microbial diversity to enhancing community compositional stability in co contaminated soils.