Bacterial communities and C-N cycling drive microplastic-specific trade-off between greenhouse gas emissions and antibiotic resistance genes during reductive soil disinfestation

Microplastics coexist with various soil degradations in intensive agricultural systems. Reductive soil disinfestation (RSD), a microbial community-based strategy, is widely used to alleviate soil degradation. However, microplastics' impact on soil bacterial communities and C-N cycling during RSD remains unclear, with such changes potentially further affecting greenhouse gas emissions and the prevalence of antibiotic resistance genes (ARGs). A microcosm experiment was conducted using biodegradable poly(butylene adipate-co-terephthalate) (PB) and non-degradable polyethylene (PE), with six treatments: untreated control (CK), PB- or PE-amended soil (PB, PE), straw incorporation with flooding (RSD), and RSD combined with PB or PE (PBRSD, PERSD). Results showed that compared to CK, RSD increased CH₄ emissions by 12-fold without affecting CO₂, whereas PBRSD enhanced both by 20-fold and 29 %, respectively, while PERSD increased CH₄ by 6.1-fold. Though RSD elevated N₂O emissions by 89 % relative to CK, microplastics mitigated this increase by 29 % in PBRSD and 17 % in PERSD. RSD reduced soil ARG abundance from 0.18 % (CK) to 0.16 %, with PBRSD intensifying this reduction but PERSD counteracted it. Enrichment of key bacterial taxa (e.g., Clostridium, Paenibacillus) was closely linked to the coregulation of ARGs (multidrug, aminoglycoside) and C-N cycling processes (pyruvate metabolism, methanogenesis, denitrification). Collectively, under RSD, PB enhanced greenhouse gas emissions but reduced ARGs, whereas PE mitigated greenhouse gas emissions yet promoted ARG accumulation, driven by shifts in bacterial communities and C-N cycling. These findings reveal a bacterial community and C-N cycling driven microplastic-specific trade-off between greenhouse gas emissions and ARGs control under RSD, informing sustainable soil management.