Metagenomic surveillance of temperature-drived bacterial threats to drinking water safety

Climate warming may exacerbate the risk of pathogenic bacteria and antibiotic resistance genes (ARGs) in aquatic environments. However, research on the impact of climate warming on bacterial pathogenic risks and virulence factors (VFs) communities in drinking water sources remains scarce. This study combined field multi-season monitoring with controlled laboratory temperature simulation experiments. Using 16S rRNA and metagenomic sequencing, we investigated the effects of gradually increasing temperature on pathogenic bacteria and VF community in the Gan River source area. A significant positive correlation with temperature was observed in the seasonal shifts of Legionella, Mycobacterium, and Pseudomonas during field multi-season monitoring. Our laboratory temperature simulation experiments further illustrated the differential modulation of temperature on opportunistic pathogens and their VFs. The abundance of 9 specific VFs was significantly associated with temperature. Within the high-temperature range (35-40 °C), Legionella showed a synergistic increase in both its population and the abundance of its VF (Hsp60); Mycobacterium's VF (NuoG) abundance increased significantly with increasing temperature, while the population size remained stable. Furthermore, 3 key bacterial infectious disease pathways- Bacterial invasion of epithelial cells, Staphylococcus aureus infection, and Vibrio cholerae infection were significantly enriched with elevated temperature. Furthermore, high temperatures may also weaken the microbial inactivation efficiency of the conventional chlorine disinfection process, thereby posing a potential threat to drinking water safety. This study elucidates how elevated temperature is linked to the enhanced pathogenic potential of opportunistic pathogens, mediated through the differential regulation of VFs. This provides a scientific basis for assessing aquatic microbial risks under climate warming.