[Effects of Typical Microplastics on Methanogenesis and Antibiotic Resistance Genes in Anaerobic Digestion of Sludge]

Waste sludge is an important carrier of antibiotic resistance genes （ARGs） and an important place for the enrichment of microplastics （MPs）. To explore the impacts of typical MPs on sludge recycling and harmless disposal, the effects of polyamide （PA）, polyethylene （PE）, and polypropylene （PP） MPs on the methanogenesis efficiency of anaerobic digestion were investigated. Meanwhile, based on metagenomic sequencing, the effects of MPs on ARGs, mobile genetic elements （MGEs）, microbial community structure, and host bacteria during anaerobic digestion were analyzed. The results showed that PA-MPs, PE-MPs, and PP-MPs increased the distribution of methane production by 2.2%, 22.3%, and 28.8%, respectively. MPs promoted methanation by improving the dissolution and hydrolysis efficiency of organic matter, and the enrichment of hydrogenotrophic methanogens by PP-MPs further improved the methanogenic efficiency. PA-MPs contributed to the removal of ARGs, while PE-MPs and PP-MPs had adverse effects on the reduction of ARGs. Horizontal gene transfer mediated by integron and insertion sequences was an important factor in the spread of ARGs. Proteobacteria was the key host leading to the diffusion of ARGs. The removal of pathogens from Bacteroidetes by anaerobic digestion contributed to the reduction of ARGs. The selective enrichment or inhibition of Arenimonas, Acinetobacter, Actinobacillus, Nitrospira, and other important host bacteria by MPs was the major cause for the difference in the removal effect of ARGs.