The beneficial use of nanoparticle silver or nanosilver may be confounded when its potent antimicrobial properties impact non-target members of natural microbiomes such as those present in soil or the plant rhizosphere. Agricultural soils are a likely sink for nanosilver due to its presence in agrochemicals and land-applied biosolids, but a complete assessment of nanosilver’s effects on this environment is lacking because the impact on the natural soil microbiome is not known. In a study assessing the use of nanosilver for phytopathogen control with maize, we analyzed the metatranscriptome of the maize rhizosphere and observed multiple unintended effects of exposure to 100 mg kg−1 nanosilver in soil during a growth period of 117 days. We found several unintended effects of nanosilver which could interfere with agricultural systems in the long term. Firstly, the archaea community was negatively impacted with a more than 30% decrease in relative abundance, and as such, their involvement in nitrogen cycling and specifically, nitrification, was compromised. Secondly, certain potentially phytopathogenic fungal groups showed significantly increased abundances, possibly due to the negative effects of nanosilver on bacteria exerting natural biocontrol against these fungi as indicated by negative interactions in a network analysis. Up to 5-fold increases in relative abundance have been observed for certain possibly phytopathogenic fungal genera. Lastly, nanosilver exposure also caused a direct physiological impact on maize as illustrated by increased transcript abundance of aquaporin and phytohormone genes, overall resulting in a stress level with the potential to yield hormetically stimulated plant root growth. This study indicates the occurrence of significant unintended effects of nanosilver use on corn, which could turn out to be negative to crop productivity and ecosystem health in the long term. We therefore highlight the need to include the microbiome when assessing the risk associated with nano-enabled agriculture.

中文翻译：

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通过元转录组分析玉米的纳米颗粒处理：氮循环受损、可能的植物病原体选择和植物兴奋作用。

当纳米颗粒银或纳米银的有效抗菌特性影响天然微生物组的非目标成员（例如土壤或植物根际中存在的微生物）时，其有益用途可能会被混淆。由于农用化学品和土地施用的生物固体中存在纳米银，农业土壤可能是纳米银的汇，但由于纳米银对自然土壤微生物组的影响尚不清楚，因此缺乏对纳米银对这种环境影响的完整评估。在一项评估纳米银用于玉米植物病原体控制的研究中，我们分析了玉米根际的元转录组，并观察到在 117 天的生长期期间土壤中暴露于 100 mg kg−1 纳米银的多种意想不到的影响。我们发现纳米银的一些意想不到的影响可能会长期干扰农业系统。首先，古细菌群落受到负面影响，相对丰度下降了 30% 以上，因此，它们对氮循环（特别是硝化作用）的参与受到损害。其次，某些潜在植物病原真菌群的丰度显着增加，这可能是由于纳米银对对这些真菌发挥天然生物防治作用的细菌产生了负面影响，正如网络分析中的负面相互作用所表明的那样。对于某些可能致病的真菌属，已观察到相对丰度增加了 5 倍。最后，纳米银暴露还对玉米产生了直接的生理影响，如水通道蛋白和植物激素基因的转录本丰度增加所示，总体上导致了胁迫水平，有可能产生毒效刺激植物根部生长。这项研究表明，纳米银的使用对玉米产生了重大的意想不到的影响，从长远来看，这可能会对作物生产力和生态系统健康产生负面影响。因此，我们强调在评估与纳米农业相关的风险时需要将微生物组包括在内。