The present study investigated the effect of single as well as a mixture of nanoparticles (ZnO and CuO NPs) on algae–bacteria consortia using the OECD 96-h toxicity test, one of the first efforts as per the authors' knowledge. Microalgae (Scenedesmus obliquus) and bacteria (Escherichia coli) were used as test organisms in OECD media. Effects of the different concentrations of NPs (0, 0.1 mg L⁻¹, 1 mg L⁻¹, 10 mg L⁻¹, and 100 mg L⁻¹) on 3 algae–bacteria ratios (1 : 1, 1 : 100 and 100 : 1) were studied using parameters, such as chlorophyll, biomass, lipid, and protein contents, reactive oxygen species (ROS) generation, and extracellular polymeric substance (EPS) components. At environmentally relevant NP concentration (0.1 mg L⁻¹), the order of toxicity of NPs to algae–bacteria consortia was found to be: CuO NPs (highest toxicity) > ZnO + CuO NPs > ZnO NPs (least toxicity). At 100 mg L⁻¹ NP concentration, structural changes and cell leakage in the samples containing NPs with algae–bacteria consortia were observed during TEM analysis. FTIR (Fourier transform infra-red) analysis indicated the addition of bonds and a difference in the peak location and its intensity values. The corresponding metal ions (Zn and Cu ions) resulted in higher toxicity to algae–bacteria consortia than metal oxide NPs. When nanoparticles were interacting with the algae–bacteria consortia in the suspension, it was observed that by absorption and dissolution, nanoparticles would enter inside the algal and bacterial cells simultaneously, altering the surface charge of the cell membrane. Due to the formation of EPSs, some of the nanoparticles would not be able to enter the cell cytoplasm but would interact with the EPS. ROS generation would take place extracellularly as well as intracellularly due to the interaction of nanoparticles. Overall, the mixture of NPs at environmentally relevant concentrations (<1 mg L⁻¹) poses lower toxicity to algae–bacteria consortia than individual nanoparticles. More experimental studies need to be performed to understand the effect of NPs on the functioning of algae–bacteria consortia for effective wastewater treatment using algae–bacteria consortia.

中文翻译：

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纳米粒子混合物对 OECD 介质中藻类-细菌菌群的毒性

本研究使用 OECD 96 小时毒性测试研究了单一纳米颗粒以及纳米颗粒混合物（ZnO 和 CuO NP）对藻类-细菌群落的影响，这是据作者所知的首批努力之一。微藻（斜生栅藻）和细菌（大肠杆菌）被用作 OECD 培养基中的测试生物。不同浓度的纳米粒子（0、0.1 mg L ^-1、1 mg L ^-1、10 mg L ^-1和100 mg L ^-1）对3种藻菌比（1:1、1:100和100 : 1) 使用叶绿素、生物量、脂质和蛋白质含量、活性氧 (ROS) 生成和细胞外聚合物 (EPS) 成分等参数进行研究。在环境相关的纳米粒子浓度（0.1 mg L ^-1）下，纳米粒子对藻类-细菌菌群的毒性顺序为：CuO NPs（毒性最高）> ZnO + CuO NPs > ZnO NPs（毒性最小）。在 100 mg L ^-1 NP 浓度下，在 TEM 分析过程中观察到含有藻类-细菌聚生体的 NP 样品的结构变化和细胞渗漏。 FTIR（傅里叶变换红外）分析表明键的添加以及峰位置及其强度值的差异。相应的金属离子（锌离子和铜离子）对藻类-细菌群落的毒性比金属氧化物纳米颗粒更高。当纳米粒子与悬浮液中的藻类-细菌菌群相互作用时，观察到通过吸收和溶解，纳米粒子会同时进入藻类和细菌细胞内部，改变细胞膜的表面电荷。由于 EPS 的形成，一些纳米颗粒将无法进入细胞质，但会与 EPS 相互作用。由于纳米粒子的相互作用，ROS 的产生将发生在细胞外和细胞内。总体而言，环境相关浓度（<1 mg L ^-1 ）的纳米颗粒混合物对藻类-细菌群落的毒性低于单个纳米颗粒。需要进行更多的实验研究来了解纳米颗粒对藻类-细菌菌群功能的影响，以便利用藻类-细菌菌群进行有效的废水处理。