Dynamics of soil resistome and bacterial composition following multi-year application of different antibiotic fermentation residues

Antibiotic fermentation residue (AFR) is a byproduct of the antibiotic fermentation process, and its application could provide plentiful nutrients to the soil. However, the fate of antibiotic resistance genes (ARGs) in soil with consecutive repeated application of different AFRs is not fully understood. Hence, the succession of bacterial community and ARGs following the repeated application of three different AFRs (erythromycin fermentation residue (EFR), cephalosporin C fermentation residue (CFR) and penicillin fermentation residue (PFR)) was investigated. Herein, AFR after industrial-scale treatment was applied to the actual field for three consecutive years with the dosage of 7500 kg/hm². Results implied that AFR application affected the bacterial community structure over time. And treated CFR and PFR induced substantial shifts in bacterial community compared to the treated EFR. Additionally, AFR influenced the ARGs abundance, where addition of treated EFR and PFR resulted in a more prominent increase of ARGs over time compared to the treated CFR, suggesting that the consecutive repeated AFR application might pose potential risks to the persistence and spread of ARGs. Finally, duration time contributed most to the soil ARGs profiles. These findings provided insights into the dynamics of soil ARGs following the consecutive repeated application of different AFRs.