Migration characteristics of ARGs from pig manure in compost - soil - lettuce

This study aims to reveal the contamination patterns, persistence characteristics, and fate dynamics of ARGs during aerobic composting of swine manure with different carbon-nitrogen ratios (C/N = 15:1, 25:1, 35:1) and their subsequent dissemination in soil-plant systems following fertilization. The absolute abundances of 101 ARGs of six categories ranged from 10⁵ to 10¹⁴ copies/g during the composting process. The tetracyclines, macrolides and β-lactams ARGs were effectively reduced by the maturation phase. Among them, the β-lactam ARGs had the highest abatement efficiency (73-89 %). Quinolones, aminoglycosides and sulfonamides ARGs had relatively high residues during the maturation phase. Composting treatments with higher C/N (25:1 and 35:1) exhibited superior performance in ARGs reduction. Metagenomic analysis revealed the compost microbial community succession from Firmicutes to Proteobacteria and Actinobacteria. Luteimonas may be potential hosts for high-residual ARGs in compost, while Acinetobacter exhibited strong associations with β-lactam and macrolide ARGs that can be easily reduced. The ARGs in the fertilized soil increased significantly. ARGs such as floR, tetG-01, sul1 and sul2 have the highest abundance in the soil where lettuce is grown. The ARGs reduction is better in C/N 25:1 group, and the ARGs abundance of the soil is lower after fertilization with compost products. The sulfonamide sul1 and sul2 genes have always maintained a high abundance in compost, soil and lettuce. This study provides a theoretical basis for controlling the residue and spread of ARGs by regulating the C/N of compost to drive changes in microbial community.