Key factors driving the fate of antibiotic resistance genes and controlling strategies during aerobic composting of animal manure: A review

Occurrence of antibiotic resistance genes (ARGs) in animal manure impedes the reutilization of manure re-sources. Aerobic composting is potentially effective method for resource disposal of animal manure, but the fate of ARGs during composting is complicated due to the various material sources and different operating con-ditions. This review concentrates on the biotic and abiotic factors influencing the variation of ARGs in composting and their potential mechanisms. The dynamic variations of biotic factors, including bacterial community, mobile genetic elements (MGEs) and existence forms of ARGs, are the direct driving factors of the fate of ARGs during composting. However, most key abiotic indicators, including pH, moisture content, antibiotics and heavy metals, interfere with the richness of ARGs indirectly by influencing the succession of bacterial community and abun-dance of MGEs. The effect of temperature on ARGs depends on whether the ARGs are intracellular or extracellu-lar, which should be paid more attention. The emergence of various controlling strategies renders the composting products safer. Four potential removal mechanisms of ARGs in different controlling strategies have been con-cluded, encompassing the attenuation of selective/co-selective pressure on ARGs, killing the potential host bac-teria of ARGs, reshaping the structure of bacterial community and reducing the cell-to-cell contact of bacteria. With the effective control of ARGs, aerobic composting is suggested to be a sustainable and promising approach to treat animal manure. (c) 2021 Elsevier B.V. All rights reserved.