resistomes and microbiomes during carcass decomposition

Serious concerns have been raised regarding resistoms causing by corpse decomposition in aquatic environment, which poses huge threats to public health and water quality. However, antibiotic resistance genes (ARGs) in the large volume of water and large time scale are poorly explored. In this study, high-throughput quantitative PCR (HT-qPCR) was applied to profile ARGs and mobile genetic elements (MGEs). High-throughput sequencing was used for bacterial communities in experimental and control groups all containing 50 L tap water at 7, 15, 100 days of corpse decomposition. Our results showed environmental factors especially pH, dissolve oxygen (DO) and conductivity were significantly correlated with the abundance of ARGs during corpse decomposition (P < 0.05). Twelve opportunistic pathogens especially Burkholderia, Legionella and Halomonas remarkably increased initially and gradually approached normal level when decomposition processed. The gene copy numbers of 56 ARGs and 8 MGEs including 6 transposons and 2 integrons were detected, which showed obviously higher abundance compared with the control groups. The absolute abundance of ARGs in the experimental groups were even enriched from 259 to 413,640-folds compared with control groups on the 15 days of corpse decomposition. In addition, DO and pH were important factors in influencing microbial community and all detected ARGs and opportunistic pathogens were significantly associated with ARGs. These results emphasize that MGEs, opportunistic pathogens and environmental factors might have remarkably influenced the distribution and abundance of ARGs in the large volume of tap water during corpse decomposition. Our study offers a novel insight into research for ARGs and MGEs in the large volume of water environment, highlighting the relationship among opportunistic pathogens, environmental factors, MGEs and ARGs and thereby uncovering the harmful effects of cadavers in aquatic environment.