Enhanced suppression effects on Microcystis aeruginosa by combining hydrogen peroxide and intermittent UVC...

In order to strengthen the inhibitory effect of UVC/H₂O₂ on Microcystis aeruginosa growth, this study designed a novel strategy for inducing an advanced oxidation process in algal cells by splitting UVC irradiation into two rounds. The first irradiation of UVC upon adding H₂O₂ facilitated the delivery of H₂O₂ into the cell cytoplasm, which induced an intracellular advanced oxidation process after the second irradiation of UVC. The intermittent treatment of UVC/H₂O₂ could further attack the Ca-Mn and Fe-S clusters in the photosynthetic electron transport chain. In contrast, conventional simultaneous treatment of UVC/H₂O₂ only attacked the interaction subunits between PSII cores and the phycobilisome. The block of the photosynthetic electron transport chain, shedding of the Ca-Mn cluster, and damage of the Fe-S cluster gave rise to massive intracellular H₂O₂, O₂^•-, and HO•. Consequently, ROS acted as a mediator and led to caspase-3(-like) activation and the subsequent initiation of apoptosis-like cell death. The remarkable functional mechanisms make the intermittent treatment of UVC/H₂O₂ an ideal method for the practical application of suppressing HABs (target-selective, long-lasting, cost-minimized, and eco-friendly).