Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China; Key Laboratory of Hydraulic and Waterway Engineering, Ministry of Education, Chongqing Jiaotong University, Chongqing 400074, China; Lingzhi Environmental Protection Co., Ltd, Wuxi 214200, China.
Key Laboratory of Eco-Environment of Three Gorges Region, Ministry of Education, Chongqing University, Chongqing 400044, China.
Ecotoxicol Environ Saf. 2021 Oct 1;222:112496. doi: 10.1016/j.ecoenv.2021.112496. Epub 2021 Jul 7.
Antibiotics are frequently detected in aquatic ecosystems, posing a potential threat to the freshwater environment. However, the response mechanism of freshwater microalgae to antibiotics remains inadequately understood. Here, the impacts of azithromycin (a broadly used antibiotic) on microalgae Chlorella pyrenoidosa were systematically studied. The results revealed that high concentrations (5-100 μg/L) of azithromycin inhibited algal growth, with a 96-h half maximal effective concentration of 41.6 μg/L. Azithromycin could weaken the photosynthetic activities of algae by promoting heat dissipation, inhibiting the absorption and trapping of light energy, impairing the reaction centre, and blocking electron transfer beyond Q. The blockage of the electron transport chain in the photosynthetic process further induced the generation of reactive oxygen species (ROS). The increases in the activities of superoxide dismutase, peroxidase and glutathione played important roles in antioxidant systems but were still not enough to scavenge the excessive ROS, thus resulting in the oxidative damage indicated by the elevated malondialdehyde level. Furthermore, azithromycin reduced the energy reserves (protein, carbohydrate and lipid) and impaired the cellular structure. In contrast, a hormesis effect on algal growth was found when exposed to low concentrations (0.5 and 1 μg/L) of azithromycin. Low concentrations of azithromycin could induce the activities of the PSII reaction centre by upregulating the mRNA expression of psbA. Additionally, increased chlorophyll b and carotenoids could improve the absorption of light energy and decrease oxidative damage, which further contributed to the increase in energy reserves (protein, carbohydrate and lipid). The risk quotients of azithromycin calculated in this study were higher than 1, suggesting that azithromycin could pose considerable ecological risks in real environments. The present work confirmed that azithromycin induced dual effects on microalgae, which provided new insight for understanding the ecological risk of antibiotics.
抗生素经常在水生生态系统中被检测到，对淡水环境构成潜在威胁。然而，淡水微藻对抗生素的响应机制仍未得到充分理解。在这里，系统研究了阿奇霉素（一种广泛使用的抗生素）对微藻蛋白核小球藻的影响。结果表明，高浓度（5-100μg/L）的阿奇霉素抑制藻类生长，96 小时半最大有效浓度为 41.6μg/L。阿奇霉素通过促进热耗散、抑制光能吸收和捕获、损伤反应中心以及阻断 Q 点之后的电子传递来削弱藻类的光合作用活性。光合作用过程中电子传递链的阻断进一步诱导活性氧（ROS）的产生。超氧化物歧化酶、过氧化物酶和谷胱甘肽活性的增加在抗氧化系统中发挥了重要作用，但仍不足以清除过多的 ROS，从而导致丙二醛水平升高所指示的氧化损伤。此外，阿奇霉素降低了能量储备（蛋白质、碳水化合物和脂质）并破坏了细胞结构。相比之下，当暴露于低浓度（0.5 和 1μg/L）的阿奇霉素时，对藻类生长表现出一种毒物兴奋效应。低浓度的阿奇霉素可以通过上调 psbA 的 mRNA 表达来诱导 PSII 反应中心的活性。此外，增加的叶绿素 b 和类胡萝卜素可以改善光能吸收并减少氧化损伤，从而进一步有助于增加能量储备（蛋白质、碳水化合物和脂质）。本研究中计算的阿奇霉素风险商数高于 1，表明阿奇霉素在实际环境中可能会带来相当大的生态风险。本研究证实，阿奇霉素对微藻产生了双重影响，为理解抗生素的生态风险提供了新的见解。
