Deciphering the influence pathway of selenium on antibiotic resistance genes during goat manure composting

Co-composting of selenium and livestock manure is an effective way to produce selenium-rich organic fertilizer. However, antibiotic resistance genes (ARGs), as emerging contaminants in compost, respond to selenium remains unknown. In this study, the effects of selenite and selenate on ARGs during goat manure composting were investigated. Compared to the control, the abundance of ARGs decreased by 8.39% with selenate addition, whereas increasing by 9.75% with selenite addition. ARGs degradation in selenate-added treatment was driven by a succession of potential hosts, primarily including Proteobacteria. Meanwhile, mobile genetic elements, oxidative stress response and type IV secretion system genes were down-regulated following selenate exposure, inhibiting the transmission of ARGs through horizontal gene transfer. Both selenite and selenate reduced the aminoglycoside and beta-lactam resistance genes while enriching the multidrug resistance genes in compost. In conclusion, selenate improved the removal of ARGs and was recommended for producing selenium-rich organic fertilizer.