Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus of Gualtar, 4710-057, Braga, Portugal; Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus of Gualtar, 4710-057, Braga, Portugal.
Environ Pollut. 2021 Jan 1;268(Pt B):115913. doi: 10.1016/j.envpol.2020.115913. Epub 2020 Oct 22.
Silver nanoparticles (AgNPs) are among the major groups of contaminants of emerging concern for aquatic ecosystems. The massive application of AgNPs relies on the antimicrobial properties of Ag, raising concerns about their potential risk to ecologically important freshwater microbes and the processes they drive. Moreover, it is still uncertain whether the effects of AgNPs are driven by the same mechanisms underlying those of Ag ions (Ag). We employed transcriptomics to better understand AgNP toxicity and disentangle the role of Ag in the overall toxicity towards aquatic fungi. To that end, the worldwide-distributed aquatic fungus Articulospora tetracladia, that plays a central role in organic matter turnover in freshwaters, was selected and exposed for 3 days to citrate-coated AgNPs (∼20 nm) and Ag at concentrations inhibiting 20% of growth (EC). Responses revealed 258 up- and 162 down-regulated genes upon exposure to AgNPs and 448 up- and 84 down-regulated genes under exposure to Ag. Different gene expression patterns were found after exposure to each silver form, suggesting distinct mechanisms of action. Gene ontology (GO) analyses showed that the major cellular targets likely affected by both silver forms were the biological membranes. GO-based biological processes indicated that AgNPs up-regulated the genes involved in transport, nucleobase metabolism and energy production, but down-regulated those associated with redox and carbohydrate metabolism. Ag up-regulated the genes involved in carbohydrate and steroid metabolism, whereas genes involved in localization and transport were down-regulated. Our results showed, for the first time, distinct profiles of gene expression in aquatic fungi exposed to AgNPs and Ag, supporting different modes of toxicity of each silver form. Also, our results suggest that Ag had a negligible role in the toxicity induced by AgNPs. Finally, our study highlights the power of transcriptomics in portraying the stress induced by different silver forms in organisms.
银纳米粒子（AgNPs）是水生生态系统中新兴关注的主要污染物之一。AgNPs 的大规模应用依赖于 Ag 的抗菌特性，这引发了人们对其对生态重要的淡水微生物及其驱动的过程潜在风险的担忧。此外，AgNPs 的影响是否由 Ag 离子（Ag）的相同机制驱动仍不确定。我们采用转录组学来更好地理解 AgNP 的毒性，并阐明 Ag 在整体毒性对水生真菌中的作用。为此，选择了在淡水中广泛分布的真菌 Arthrospira tetracladia，该真菌在有机物质转化中发挥着核心作用，并将其暴露于 3 天内，使其接触柠檬酸包覆的 AgNPs（∼20nm）和浓度为 20%生长抑制浓度（EC）的 Ag。暴露于 AgNPs 和 Ag 后，分别有 258 个上调和 162 个下调基因，以及 448 个上调和 84 个下调基因。每种银形态暴露后发现了不同的基因表达模式，表明存在不同的作用机制。GO 分析表明，两种银形态可能影响的主要细胞靶标是生物膜。基于 GO 的生物过程表明，AgNPs 上调了与运输、核碱基代谢和能量产生相关的基因，但下调了与氧化还原和碳水化合物代谢相关的基因。Ag 上调了与碳水化合物和类固醇代谢相关的基因，而与定位和运输相关的基因则下调。我们的研究结果首次表明，暴露于 AgNPs 和 Ag 的水生真菌表现出不同的基因表达谱，支持每种银形态具有不同的毒性模式。此外，我们的研究结果表明，Ag 在 AgNPs 诱导的毒性中作用可以忽略不计。最后，我们的研究强调了转录组学在描绘不同银形态对生物体产生的应激方面的强大功能。
