To elucidate the potential ecological risks of carbon dots, a novel nanomaterial, this study investigated the physiological responses and underlying mechanisms of the freshwater microalgae Euglena gracilis following exposure to pristine carbon dots(CDs)and Cu-N-doped carbon dots(Cu-CDs). The results demonstrated that both types of carbon dots initially promoted but subsequently inhibited the growth of E. gracilis over time. Compared to CDs, Cu-CDs exerted a more pronounced impact on key physiological processes, including photosynthesis and antioxidant defense. Exposure to 1mg/L and 10mg/L Cu-CDs resulted in the accumulation of photosynthetic pigments and a decline in photosystem II activity, whereas a significant change in photosynthetic pigment content was observed only at 10mg/L in the CDs-exposed group. The maximum inhibition rates of superoxide dismutase activity induced by CDs and Cu-CDs were 62.52% and 78.35%, respectively. Metabolomics analysis further confirmed that Cu-CDs triggered a stronger metabolic disturbances, with the most notable alterations observed in lipid metabolism pathways, indicating compromised membrane stability of E. gracilis. Disruptions in amino acid and photosynthetic metabolism pathways were primarily attributed to oxidative stress. Additionally, both CDs and Cu-CDs affected energy metabolism by altering in alanine, aspartate, and glutamate metabolism, as well as glycolysis/gluconeogenesis pathways. Overall, the impairment of photosynthetic and antioxidant system may represent the primary toxic mechanisms of carbon dots in E. gracilis.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |