Beyond inactivation: wavelength-dependent regulation of VBNC formation and resuscitation risk in photochemical disinfection.

Photochemical disinfection is increasingly applied in water treatment because of its broad-spectrum antimicrobial activity. However, current evaluations primarily focus on inactivation kinetics while post-treatment microbial behaviors such as viable but non-culturable (VBNC) state formation and resuscitation remain poorly understood. Here we show that irradiating 2,3-butanedione (BD) with ultraviolet (UV) or visible (Vis) light generated similar oxidative stress but induced fundamentally different cellular outcomes. UV/BD achieved rapid inactivation but predominantly induced a VBNC state. In contrast, Vis/BD required prolonged irradiation yet resulted in cell death and complete loss of resuscitation potential. The distinct wavelength-dependent adaptation strategies were further revealed through transcriptomic analyses. UV/BD triggered metabolic reprogramming, allowing maintenance of basal energy supply and therefore survival in a dormant state. In contrast, Vis/BD simultaneously suppressed energy-generating pathways and induced extensive activation of ribosomal biogenesis, transcriptional machinery, sulfur metabolism, and repair-related processes. This maladaptive overactivation accelerated ATP exhaustion and metabolic collapse, ultimately driving cell death. These findings establish a wavelength-directed microbial fate framework in which transcriptional strategy and energy homeostasis, rather than oxidative stress intensity alone, govern the transition between dormancy and death.