Deciphering the molecular mechanisms of Microcystis aeruginosa eradication by didecyl methyl propyl ammonium iodide: A combined transcriptomic and physiological approach

Global concern is rising over the harmful impact of cyanobacterial blooms. Chemical prevention has broad prospects in controlling cyanobacterial blooms. Didecyl methyl propyl ammonium iodide (DMPAI) has been proven to be an effective and relatively safe reagent for controlling Microcystis blooms, with its efficacy in pilot test field applications already verified. In our research, field - scale killing experiments were carried out, and by means of transcriptomic and physiological experiments, we investigated the algicidal mechanism of DMPAI against Microcystis aeruginosa. The field experiments demonstrated that DMPAI exhibits a remarkable algicidal effect on M. aeruginosa. Microscopic analysis disclosed that DMPAI treatment caused surface depressions and cell lysis in cyanobacterial cells. OJIP transient measurements revealed that DMPAI at 0.5 mg/L caused marked elevation of the J-step (at ~2 ms) and I-step (at ~30 ms) in the fluorescence induction curve. Biochemical analysis showed that DMPAI treatment initially increased antioxidant enzyme activities and MDA levels, followed by a decrease. The transcriptomic analysis revealed that under DMPAI treatment, a total of 158 genes exhibited significant changes. Key findings show a marked downregulation of glutathione peroxidase, decreased molecular chaperones, increased ATPases, and notable changes in photosystem II proteins. The comprehensive results suggests that DMPAI inhibits M. aeruginosa by impairing the antioxidant system, damaging membrane lipid proteins, impacting energy synthesis, and hindering photosynthetic capacity, thus showing strong algicidal effectiveness. These findings highlight DMPAI's potent algicidal properties and its potential application in controlling cyanobacterial blooms, which may contribute to future environmental management strategies.