Temporal decoupling between cyanobacterial inactivation and microcystin release under radiation-induced oxidative...

This study investigates the environmental transformation behavior of Microcystis aeruginosa and associated microcystin under gamma irradiation-induced oxidative stress, with emphasis on toxin dynamics in aquatic systems. Hydroxyl radicals (•OH) generated during irradiation preferentially targeted photosynthetic pigments and protein complexes, leading to metabolic impairment and oxidative stress-mediated cellular collapse characterized by increased SOD and CAT activities, ROS accumulation, and reduced membrane permeability. Analysis of extracellular exudates showed a protein-dominant P/C ratio, indicating progressive oxidative modification of intracellular macromolecules prior to cell lysis. Despite pronounced metabolic disruption, intracellular microcystin concentrations remained relatively stable immediately after irradiation, demonstrating temporal decoupling between cyanobacterial inactivation and acute toxin release. Comparative analysis further revealed a structure = dependent transformation pattern, in which MC-LR exhibited greater susceptibility to radical attack than MC-RR, attributable to difference in charge distribution and hydration shell protection. These findings provide mechanistic insight into radiation-driven oxidative processes and their influence on toxin fate, establishing a framework for understanding pollutant transformation and toxin dynamics under radiolytic stress in aquatic environments.