Environment can be affected by a variety of micropollutants. In this paper, we develop a system to assess the toxicity on an environmental sample, based on the expression of a nanoluciferase under the control of the STB5 promotor in a yeast. The STB5 gene encodes for a transcription factor involved in a pleiotropic drug resistance and in the oxidative stress response. The response of the modified yeast was assessed using 42 micropollutants belonging to different families (antibiotics, pain killers, hormones, plasticizers, pesticides, etc.). Among them, 26 induced an increase of the bioluminescence for concentration ranges from pg.L⁻¹ to ng.L⁻¹. Surprisingly, for concentrations higher than 100 ng.L⁻¹, no response can be observed, suggesting that other mechanisms are involved when the stress increases. Analyzing the different responses obtained, we highlighted six nonmonotonic types of responses. The type of response seems to be independent of the properties of the compounds (polarity, toxicology, molecular weight) and of their family.

In conclusion, we highlighted that a cellular response exists for very low exposition to environmental concentration of micropollutants and that it was necessary to explore the cellular mechanisms involved at very low concentration to provide a better risk assessment.

环境会受到各种微污染物的影响。在本文中，我们开发了一个系统来评估环境样品的毒性，基于酵母中STB5启动子控制下的纳米荧光素酶的表达。所述STB5转录因子基因编码参与的多效药物抗性和在氧化应激反应。使用属于不同家族的 42 种微污染物（抗生素、止痛药、激素、增塑剂、杀虫剂等）评估了改良酵母的反应。其中，26 诱导生物发光的浓度范围从 pg.L ^-1到 ng.L ^{-1 的增加}。令人惊讶的是，对于高于 100 ng.L ^{-1 的}浓度，没有观察到反应，表明压力增加时涉及其他机制。分析获得的不同反应，我们强调了六种非单调类型的反应。反应的类型似乎与化合物的特性（极性、毒理学、分子量）及其家族无关。

总之，我们强调，在微污染物环境浓度极低的情况下存在细胞反应，并且有必要探索极低浓度下所涉及的细胞机制，以提供更好的风险评估。