Influence of the triazole fungicide difenoconazole on soil microbial communities, antibiotic resistance genes, and pathogens

Abstract

Difenoconazole (DFC) is a typical triazole fungicide (one of the main fungicides in intensive agriculture), frequently detected in agricultural soils. However, the comprehensive effect of DFC on the soil ecological environment remains limited. In this study, we used metagenomic sequencing to determine the functional changes in the soil microbial communities (bacteria and fungi), antibiotic-resistance genes (ARGs), and pathogens after exposure to DFC (0.5, 1, and 5 mg kg⁻¹) for 0, 28, and 42 d. DFC exposure perturbed soil bacteria and fungi microecology stability. DFC further stimulated the bacterial genera such as Sphingomicrobium, Nocardioides, Streptomyces, Aspergillus, and Penicillium known for degrading complex compounds at 42 d. Network analysis indicated that medium to high concentrations (1 and 5 mg kg⁻¹) of DFC elevated the proportion of positive correlations (14.35 % and 2.27 %) among dominant fungal species, fostering interspecies cooperative interactions. DFC enriched the dominant microbial community involved in nutrient cycling in the soil, impacting functional genes' abundance related to these cycles (including methanogenesis, nitrification, denitrification, and nitrogen fixation). Furthermore, DFC exposure heightened the risk associated with the spread of ARGs at 42 d. The co-occurrence network revealed certain shared microorganisms, such as Bacteroidota and Actinobacteriota, as potential hosts of ARGs. The co-occurrence of potential pathogens and ARGs revealed an increased risk of pathogenicity and antibiotic resistance in potential pathogens. These findings highlight the previously overlooked environmental risks DFC poses to the soil microbial community, ARGs, and pathogens in soil ecosystems.