Nano-sized titanium dioxide (nTiO₂) is one of the most commonly used materials, however the knowledge about the molecular basis for metabolic and physiological changes in phytoplankton is yet to be explored. In the present study we use a combination of targeted metabolomics, transcriptomics and physiological response studies to decipher the metabolic perturbation in green alga Chlamydomonas reinhardtii exposed for 72 h to increasing concentrations (2, 20, 100 and 200 mg L⁻¹) of nTiO₂ with primary sizes of 5, 15 and 20 nm. Results show that the exposure to all three nTiO₂ materials induced perturbation of the metabolism of amino acids, nucleotides, fatty acids, tricarboxylic acids, antioxidants but not in the photosynthesis. The alterations of the most responsive metabolites were concentration and primary size-dependent despite the significant formation of micrometer-size aggregates and their sedimentation. The metabolic perturbations corroborate the observed physiological responses and transcriptomic results and confirmed the importance of oxidative stress as a major toxicity mechanism for nTiO₂. Transcriptomics revealed also an important influence of nTiO₂ treatments on the transport, adenosine triphosphate binding cassette transporters, and metal transporters, suggesting a perturbation in a global nutrition of the microalgal cell, which was most pronounced for exposure to 5 nm nTiO₂. The present study provides for the first-time evidence for the main metabolic perturbations in green alga C. reinhardtii exposed to nTiO₂ and helps to improve biological understanding of the molecular basis of these perturbations.

中文翻译：

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暴露于 nTiO2 材料的莱茵衣藻藻类的代谢变化

纳米二氧化钛 (nTiO ₂ ) 是最常用的材料之一，但关于浮游植物代谢和生理变化的分子基础的知识仍有待探索。在本研究中，我们结合使用靶向代谢组学、转录组学和生理反应研究来破译绿藻莱茵衣藻暴露 72 小时以增加浓度（2、20、100 和 200 mg L ^-1）的 nTiO ₂的代谢扰动主要尺寸为 5、15 和 20 nm。结果表明，暴露于所有三种 nTiO ₂材料会干扰氨基酸、核苷酸、脂肪酸、三羧酸、抗氧化剂的代谢，但不会干扰光合作用。尽管显着形成微米级聚集体及其沉降，但反应最灵敏的代谢物的变化是浓度和初级尺寸依赖性的。代谢扰动证实了观察到的生理反应和转录组学结果，并证实了氧化应激作为 nTiO ₂主要毒性机制的重要性。_{转录组学也揭示了nTiO 2}的重要影响对转运、三磷酸腺苷结合盒转运蛋白和金属转运蛋白的处理表明微藻细胞的整体营养受到干扰，这在暴露于 5 nm nTiO ₂时最为明显。本研究首次为暴露于 nTiO ₂的绿藻莱茵衣藻的主要代谢扰动提供了证据，并有助于提高对这些扰动分子基础的生物学理解。