Metabolic profiling of silver nanoparticle toxicity in Microcystis aeruginosa

The widespread use of silver nanoparticles (AgNPs) is becoming a growing concern because of the risk they pose to the ecological environment and human health. Unfortunately, little is known about how AgNPs' toxicity affects the mechanisms of metabolite shift in aquatic organisms. The aim of this work is thus to study systematically the cellular metabolism of the cyanobacteria Microcystis aeruginosa upon exposure to AgNPs by using metabolomics based on non-targeted liquid chromatography and mass spectrometry. The results reveal that a total of 97 biochemical metabolites and 16 specific metabolic pathways are significantly altered by exposure to AgNPs, many of which are associated with cellular stress response. Importantly, a metabolic analysis identified some novel metabolic pathways that are specifically regulated by AgNPs, including arginine and proline metabolism, indole alkaloid biosynthesis, and phospholipid metabolism (phosphatidylinositol-4,5-bisphosphate). Further examination revealed that exposure to AgNPs elevates superoxide dismutase activity and malondialdehyde generation, damages the thylakoids, and interrupts the endocytosis process in algae cells. Together, the manifestation of differential metabolic profiles combined with the perturbation of physiological indicators upon AgNP exposure is taken as evidence of damage to photosynthesis and membranes. These results provide holistic information about complex disturbances in metabolite profiles of M. aeruginosa upon exposure to AgNPs and provide new insights into the mechanisms of AgNPs' toxicity in the aquatic environment.