Metagenomic analysis of florfenicol and microplastics effects on microbial function and antibiotic resistome in rice seedling rhizosphere soil.

Antibiotics enrich antibiotic resistance genes (ARGs) and virulence factor genes (VFGs) in farmland, but the contribution of microplastics (MPs) to this process remains unclear. Here, through metagenome analysis, we revealed the add-on effects of PE and PLA on ARGs and VFGs enrichment in rice seedling rhizosphere soil under florfenicol (FF) stress. Compared with controls, root iron plaque content decreased by 35%, 66% and 69% under FF, FF + PE and FF + PLA treatments, disrupting microbial iron balance and activating ABC transporter pathways. Loss of beneficial/core microbes weakened community resistance; bacteria were more sensitive to stress than fungi. Among 945 ARGs and 391 VFs detected, antibiotic efflux abundance rose by 184% under FF, while mobile genetic elements (MGEs) increased from 0.5% to 38.1%, facilitating horizontal ARG transfer. In addition to horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs), our finding suggests a potential mechanism by which virulence factors (VFs) may promote ARG enrichment through the accumulation of tissue-damaging free radicals. Only one ARG-carrying human pathogen existed in controls, whereas six multi-drug-resistant pathogens emerged under combined pollution. This study provides new insights into the environmental risks of the add-on effects of MPs under antibiotics stress and contributing to the "One Health" goal.