Antibiotic degradation dominates the removal of antibiotic resistance genes during composting

To identify the key hosts involved in horizontal gene transfer (HGT) and vertical gene transfer (VGT) of antibiotic resistance genes (ARGs) and to determine the extent to and ways in which environmental properties contribute to ARG removal, the changes in ARG profile and key hosts during biogas residue and pig manure composting were investigated using metagenomic sequencing coupled with network analysis. Composting significantly reduced the abundances of ARGs other than bacA. Seventy and 41 hosts from Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes were associated with HGT and VGT, respectively. The key environmental properties were deter-mined using structural equation modelling. Antibiotics directly affected HGT and determined ARG removal. Temperature indirectly affected HGT, mainly by influencing the degradation of antibiotics. BacA was associated only with hosts involved in VGT, which may lead to its low removal rate. These findings specify the priority and pathway of antibiotics and temperature affecting ARG profile.

Automated summary

Analyzing the impact of composting on antibiotic resistance genes (ARGs) and their hosts, the study found that antibiotics directly affected horizontal gene transfer (HGT) while temperature indirectly influenced HGT through antibiotic degradation. BacA was associated only with hosts involved in vertical gene transfer (VGT), potentially explaining its low removal rate.