Fungal spore inactivation in drinking water by UV222: Kinetics and mechanistic insights with transcriptomic and metabolomic analyses

Fungal spores in drinking water distribution systems can resist chlor(am)ination and cause odor issues and health risks, posing a significant threat to drinking water safety. Conventional low-pressure mercury lamps emitting at 254 nm (UV₂₅₄) exhibit limited effectiveness against fungal spores. Far-ultraviolet light at 222 nm (UV₂₂₂) has emerged as a promising approach for efficient fungal spore inactivation. This study systematically evaluated the inactivation efficiency and omics-based mechanisms of UV₂₂₂ against Aspergillus tubingensis, Penicillium chrysogenum, and Penicillium spinulosum spores. Inactivation kinetics analysis revealed that UV₂₂₂ achieved superior inactivation compared to UV₂₅₄, reducing the UV dose required for a 3-log reduction by 28.9%–54.7%. Notably, UV₂₂₂ effectively reduced the initial shoulder effect observed during inactivation. Flow cytometric analysis further demonstrated that UV₂₂₂ induced more severe membrane damage, significantly elevated intracellular reactive oxygen species levels and induced mitochondrial membrane hyperpolarization compared to UV₂₅₄. Integrated transcriptomic and metabolomic analyses demonstrated that UV₂₂₂ markedly impaired core metabolic pathways including oxidative phosphorylation and the citrate cycle, while also suppressed the expression of DNA repair-related genes. In contrast, UV₂₅₄ primarily triggered stress responses, characterized by enhanced energy metabolism and upregulation of antioxidant-related genes, thereby increasing spore resistance to UV-induced damage. Overall, this study provides novel insights into the superior inactivation efficacy and underlying mechanisms of UV₂₂₂ in inactivating chlorine-resistant fungal spores, underscoring its potential as a promising strategy for drinking water disinfection.