Seasonal dynamics and environmental regulation of pathogenic bacteria in the Weihe River Basin

Waterborne pathogen transmission poses a significant global environmental health risk. This study employs metagenomic sequencing combined with co-occurrence network analysis, redundancy analysis (RDA), and partial least squares path modeling (PLS-PM) to investigate the distribution and transmission risk of pathogens in the Weihe River Basin. The study identified 232 pathogenic species in the Weihe River's main and tributary waters, with core pathogens (such as Pseudomonas aeruginosa and Salmonella enterica) consistently present across all hydrological periods. RDA analysis indicated temperature, salinity, nitrate-nitrogen, and chlorophyll-a are key environmental factors driving pathogen community structure. The PLS-PM model reveals significant seasonal variations in the association patterns between mobile genetic elements (MGEs) and pathogens. During the high-water period, MGEs showed the strongest correlation with pathogens, suggesting that pathogens are the primary hosts of MGEs. MGEs-mediated horizontal gene transfer may drive pathogen dissemination during this period. During the normal-water period, MGEs primarily facilitated the transfer of virulence factors (VFs), enhancing the potential pathogenicity of pathogens. During the low-water period, environmental factors promoted the spread of MGEs while inhibiting the expression of virulence genes, leading to a reduction in pathogen virulence. Co-occurrence networks further demonstrate that during the high-water period, MGEs closely linked key VFs, such as Capsule, with enteric pathogens; network connectivity decreased significantly during the normal-water period, maintaining only limited associations; during the low-water period, functional VFs were frequently co-occurring with opportunistic pathogens. This study provides scientific evidence and management references for pathogen risk assessment and control in river basins.