Temporal succession of microbiomes and resistomes during buried rat carcass decomposition

Burial is a prevalent approach for disposing of human and animal carcass. Carcass decomposition is a key natural disturbance that reshapes microbial communities and modulates biogeochemical cycles. Animal intestines serve as critical natural reservoirs of antibiotic resistance genes (ARGs), and carcass decomposition concurrently remodels intestinal bacterial assemblages and resistome profiles. Most previous studies have characterized microbial succession in surface-exposed carcasses, yet the coordinated temporal shifts of intestinal microbiota, resistomes, and horizontal gene transfer (HGT) signatures within buried carcasses remain underexplored. We established a buried rat carcass model and performed metagenomic sequencing to characterize temporal dynamics of intestinal bacteria, ARGs, mobile genetic elements (MGEs), and HGT events. Bacterial communities underwent directional succession accompanied by reduced α-diversity and stage-specific β-diversity. Proteobacteria gradually outcompeted Firmicutes and Bacteroidetes to become dominant taxa. The resistome followed regular temporal changes: tetracycline and macrolide-lincosamide-streptogramin (MLS) ARGs prevailed in early decomposition, while multidrug, β-lactam, polymyxin, and quinolone ARGs accumulated in mid-late stages, with ARG richness peaking on day 28. Approximately 83% of temporally dynamic ARG subtypes were positively correlated with decomposition duration. Procrustes analysis ( R ² = 0.859) revealed strong correlations between bacterial succession and resistome dynamics, with Proteobacteria as potential multidrug-resistant hosts and major HGT donors. This study identifies a correlative cascade of microbial succession that drives MGE functional shift, which in turn increased HGT potential and ultimately leads to resistome accumulation in buried carcass intestinal habitats. These findings expand the theoretical framework of disturbance-driven microbial-resistome co-succession and offer insights into drivers of antibiotic resistance propagation in terrestrial cadaver systems.