Physiological and molecular mechanisms of the inhibitory effects of artemisinin on Microcystis aeruginosa and Chlorella pyrenoidosa

Artemisinin , a novel plant allelochemical , has attracted attention for its potential selective inhibitory effects on algae, yet to be fully explored. This study compares the sensitivity and action targets of Microcystis aeruginosa ( M. aeruginosa ) and Chlorella pyrenoidosa ( C. pyrenoidosa ) to artemisinin algaecide (AMA), highlighting their differences. Results indicate that at high concentrations, AMA displaces the natural PQ at the Q B binding site within M. aeruginosa photosynthetic system , impairing the D1 protein repair function. Furthermore, AMA disrupts electron transfer from reduced ferredoxin (Fd) to NADP + by interfering with the iron-sulfur clusters in the ferredoxin-NADP + reductases (FNR) domain of Fd. Moreover, significant reactive oxygen species (ROS) accumulation triggers oxidative stress and interrupts the tricarboxylic acid cycle , hindering energy acquisition. Notably, AMA suppresses arginine synthesis in M. aeruginosa , leading to reduced microcystins (MCs) release. Conversely, C. pyrenoidosa counters ROS accumulation via photosynthesis protection, antioxidant defenses, and by regulating intracellular osmotic pressure , accelerating damaged protein degradation , and effectively repairing DNA for cellular detoxification . Additionally, AMA stimulates the expression of DNA replication-related genes, facilitating cell proliferation . Our finding offer a unique approach for selectively eradicating cyanobacteria while preserving beneficial algae, and shed new light on employing eco-friendly algicides with high specificity.