Uranium contamination mediating soil and ore microbial community assembly at four mining sites, South China

Uranium mining presents significant environmental challenges, particularly through radiological contamination affecting soil and water bodies. While soil microbial communities are known to be influenced by geochemical factors like pH and nutrient availability, their responses to severe uranium contamination in mine tailing environments remain poorly understood. This study investigated microbial community distributions in soils and uranium ores at four uranium mining sites in South China to explore microbial adaptations to uranium contamination. Uranium concentrations ranged from 170 to 18,000 mg/kg, with the most severely contaminated samples dominated by Cyanobacteria, which comprised up to 49.17% of the microbial community. Proteobacteria, such as Sphingomonas, were also abundant, indicating their roles in radiation resistance, while Acidobacteriota and Actinobacteria showed negative responses to uranium. Addition of lime to neutralize the acidity in mine tailings led to an increase in Gemmatimonadaceae, a family commonly found under oligotrophic conditions. Multivariate statistical analyses confirmed uranium concentration as the primary factor influencing microbial composition, along with pH values, total nitrogen, and contents of Fe₂O₃ and SiO₂ in soils. Co-occurrence network analysis suggested that extremely high uranium concentrations disrupted microbial interrelationships, reflecting communities lived more independently and adopted strategies to cope with the intense selective pressure. Intriguingly, dispersal limitation governed 90% of community assembly in high-uranium environments (>10,000 mg/kg), suggesting more isolated ecological niches. Deterministic processes such as heterogeneous and homogeneous selection only dominated the community assembly at relatively moderate to low uranium levels. These findings provide insights into the ecological dynamics of uranium-contaminated sites and related bioremediation strategies.