The effect of moisture content on dynamics changes of antibiotic resistance genes during sheep manure composting on Qinghai-Tibet Plateau: Insight into changes in potential host microorganisms

Abstract

The Qinghai-Tibet Plateau is characterized by its low temperature and thin oxygen climate, which results in hypoxic conditions during the composting of livestock and poultry manure in this region. Reducing moisture content can enhance oxygen flow through the composting pile, thereby improving humification efficiency. However, the impact of moisture content on antibiotic removal and changes in antibiotic resistance genes (ARGs) during animal manure composting on the Tibetan Plateau remains unclear. Building upon prior research, this study further investigated the dynamic changes of antibiotic concentration and ARGs during sheep manure composting on the Qinghai-Tibet Plateau at two moisture contents: 45% (M45) and 60% (M60). Additionally, the study analyzes the influencing factors and host microorganisms associated with ARGs. The results showed that, compared with M60, M45 could significantly decrease the concentrations of oxytetracycline, cephalosporin C, and penicillin in compost products by 4.37%, 3.94%, and 4.37%, respectively (P < 0.05). M45 can influence the dynamic changes of ARGs by altering the temperature, pH, total nitrogen, organic matter, humus content, and microbial communities of compost. Compared with M60, M45 reduced the abundance of ARGs conferring resistance to beta-lactam, multidrug, bacitracin, tetracycline, and vancomycin. Corynebacterium, Jeotgalicoccus, Nocardiopsis, Brachybacterium, and Arthrobacter were the main potential hosts of ARGs during the early stages of composting, whereas Streptomyces, Pseudoxanthomonas, Luteimonas, and Thermobifida became the main potential hosts during the late stages. These findings suggest that reducing moisture content can significantly enhance the removal efficiency of antibiotics and ARGs in sheep manure compost on the Qinghai-Tibet Plateau.