Increased release of engineered nanoparticles (ENPs) from widely used commercial products has threatened environmental health and safety, particularly the repeated exposures to ENPs with relatively low concentration. Herein, we studied the response of Chlorella pyrenoidesa (C. pyrenoidesa) to single and repeated exposures to silver nanoparticles (AgNPs). Repeated exposures to AgNPs promoted chlorophyll a and carotenoid production, and increased silver accumulation, thus enhancing the risk of AgNPs entering the food chain. Notably, the extracellular polymeric substances (EPS) content of the 1-AgNPs and 3-AgNPs groups were dramatically increased by 119.1% and 151.5%, respectively. We found that C. pyrenoidesa cells exposed to AgNPs had several significant alterations in metabolic process and cellular transcription. Most of the genes and metabolites are altered in a dose-dependent manner. Compared with the control group, single exposure had more differential genes and metabolites than repeated exposures. 562, 1341, 4014, 227, 483, and 2409 unigenes were differentially expressed by 1–0.5-AgNPs, 1–5-AgNPs, 1–10-AgNPs, 3–0.5-AgNPs, 3–5-AgNPs, and 3–10-AgNPs treatment groups compared with the control. Metabolomic analyses revealed that AgNPs altered the levels of sugars and amino acids, suggesting that AgNPs reprogrammed carbon/nitrogen metabolism. The changes of genes related to carbohydrate and amino acid metabolism, such as citrate synthase (CS), isocitrate dehydrogenase (IDH1), and malate dehydrogenase (MDH), further supported these results. These findings elucidated the mechanism of biological responses to repeated exposures to AgNPs, providing a new perspective on the risk assessment of nanomaterials.

中文翻译：

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转录组学和代谢组学揭示了蛋白核小球藻对不同浓度 AgNPs 单次和重复暴露的生物学反应

从广泛使用的商业产品中增加的工程纳米粒子 (ENPs) 释放已经威胁到环境健康和安全，特别是重复暴露于浓度相对较低的 ENPs。在此，我们研究了核小球藻( C. pyrenoidesa ) 对银纳米粒子 (AgNP) 单次和重复暴露的反应。反复接触 AgNPs 会促进叶绿素 a 和类胡萝卜素的产生，并增加银的积累，从而增加 AgNPs 进入食物链的风险。值得注意的是，1-AgNPs 和 3-AgNPs 组的胞外聚合物 (EPS) 含量分别显着增加了 119.1% 和 151.5%。我们发现C. pyrenoidesa暴露于 AgNPs 的细胞在代谢过程和细胞转录方面有几个显着改变。大多数基因和代谢物以剂量依赖性方式改变。与对照组相比，单次暴露比重复暴露具有更多的差异基因和代谢物。562、1341、4014、227、483 和 2409 unigenes 通过 1-0.5-AgNPs、1-5-AgNPs、1-10-AgNPs、3-0.5-AgNPs、3-5-AgNPs 和 3- 差异表达10-AgNPs 治疗组与对照组相比。代谢组学分析显示，AgNPs 改变了糖和氨基酸的水平，表明 AgNPs 重新编程了碳/氮代谢。与碳水化合物和氨基酸代谢相关的基因，如柠檬酸合酶（CS）、异柠檬酸脱氢酶（IDH1）和苹果酸脱氢酶（MDH）的变化，进一步支持了这些结果。