Microbial interactions and potential ecological implications in rain and snow: Novel insights from a semi-humid city in Northwest China

Live microorganisms dispersed through rain and snow can significantly impact urban environments, ecology and agricultural safety. The understanding of microbial interactions and ecological roles in rain and snow still remains unclear. In this study, samples from total 58 rain and snow events were collected in Xi'an, China, followed by determining the concentration, activity, and community structure of microbes. Co-occurrence networks were used to reveal interactions between microorganisms, and the functional genes within bacterial and fungal communities were also predicted. Results suggested a global trend of decreasing microbial concentrations in rain or snow with increasing latitude, while Xi'an shows a moderate level in comparison. The seasonal pattern of microbial concentration was opposite to that of activity and was significantly influenced by meteorological events. The predominant bacterial phyla were Proteobacteria (64.01 %), Bacteroidota (14.87 %), Actinobacteriota (4.50 %), while the dominant fungal phyla were Ascomycota (48.16 %) and Basidiomycota (44.40 %) in rain and snow. At the genus level, the relative abundance of dominant microbes in rain and snow was significantly correlated with the concentration of water-soluble inorganic ions. Additionally, the microbial profiles in rain exhibited significant differences between conditions with and without dust influence. Co-occurrence networks of microbes were complex, with cooperative relationships predominating. Furthermore, functional genes analysis indicated that metabolic pathways dominated bacterial communities, while plant pathogens and parasites comprised 50 % of the fungi across all seasons. These results may not only enrich our understanding of microbial seasonal dynamics in rain and snow but also highlight critical pathways through which microorganisms potentially affect ecological resilience and agricultural productivity.