Patterns of ARGs and VFs Driven by Short-Term Seasonal Hydro-Environmental Stress Interactions in a Eutrophic Plateau Lake

With the intensification of human activities, large amounts of antibiotics, heavy metals, and disinfectants enter lakes, exerting continuous selective pressure and driving the enrichment and dissemination of ARGs and VFs in aquatic microbial communities. Previous studies have primarily focused on the occurrence and abundance of ARGs in extreme plateau environments. However, the diversity and abundance of ARGs and VFs in eutrophic plateau lakes under different seasons and environmental pressures remain underexplored. In this study, we analyzed the presence of ARGs and VFs in the eutrophic plateau lake Qilu Lake across different seasons. From the perspective of hydrology and water quality, there is no inflow into the lake during the dry season, while the wet season sees an inflow of 28.1724 million cubic meters. Organic matter and metal ions are significantly higher in the dry season, whereas total nitrogen and pH levels rise notably in the wet season. We found 29 types of ARGs and 601 types of VFs in the dry season, compared to 45 types of ARGs and 637 types of VFs in the wet season. In both seasons, glycopeptide antibiotic resistance genes were the most abundant ARGs. LPS was the most abundant VFs in the dry season, while Type IV pili dominated in the wet season. The primary microbial-driven resistance mechanism strategy in both seasons was Antibiotic target alteration. The microorganism with the highest abundance of ARGs and VFs in both seasons was Pseudomonadota. Correlation analysis showed a positive relationship between the abundance of ARGs and VFs in both seasons, with this relationship being more pronounced in the dry season. Our findings indicate that the increased diversity and abundance of ARGs during the wet season may be directly linked to the heightened input of exogenous antibiotic-resistant bacteria and the promotion of plasmid conjugation transfer by hydraulic disturbances. Although VFs diversity was higher in the wet season, the low-water concentration effect and metal ion stress during the dry season significantly elevated the relative abundance of core VFs (e.g., type IV pili), resulting in the abundance of VFs per unit volume surpassing that of the wet season.