Silver nanoparticles (AgNPs) are widely incorporated in household, consumer and medical products. Their unintentional release via wastewaters raises concerns on their environmental impact, particularly for aquatic organisms and their associated bacterial communities. It is known that the microbiome plays an important role in its host’s health and physiology, e.g. by producing essential nutrients and providing protection against pathogens. A thorough understanding of the effects of AgNPs on bacterial communities and on their interactions with the host is crucial to fully assess AgNP toxicity on aquatic organisms. Our results indicate that the microbiome of the invertebrate Schmidtea mediterranea, a freshwater planarian, is affected by AgNP exposure at the tested 10 μg/ml concentration. Using targeted amplification of the bacterial 16S rRNA gene V3–V4 region, two independent experiments on the microbiomes of adult worms revealed a consistent decrease in Betaproteobacteriales after AgNP exposure, mainly attributed to a decrease in Curvibacter and Undibacterium. Although developing tissues and organisms are known to be more sensitive to toxic compounds, three independent experiments in regenerating worms showed a less pronounced effect of AgNP exposure on the microbiome, possibly because underlying bacterial community changes during development mask the AgNP induced effect. The presence of a polyvinyl-pyrrolidone (PVP) coating did not significantly alter the outcome of the experiments compared to those with uncoated particles. The observed variation between the different experiments underlines the highly variable nature of microbiomes and emphasises the need to repeat microbiome experiments, within and between physiological states of the animal.

银纳米颗粒（AgNPs）已广泛应用于家用，消费和医疗产品中。它们无意中通过废水释放引起了人们对其环境影响的关注，特别是对水生生物及其相关细菌群落。众所周知，微生物组在其宿主的健康和生理中起着重要作用，例如通过产生必需的营养物并提供针对病原体的保护。全面了解AgNP对细菌群落及其与宿主的相互作用的影响对于全面评估AgNP对水生生物的毒性至关重要。我们的结果表明，无脊椎动物Schmidtea mediterranea的微生物组，一种淡水涡虫，受测试的10μg/ ml浓度的AgNP暴露影响。使用针对细菌的16S rRNA基因V3-V4区域进行定向扩增，对成虫的微生物群进行的两个独立实验显示，暴露于AgNP后Betaproteobacteriales持续减少，这主要归因于弯曲杆菌和双歧杆菌的减少。尽管已知发育中的组织和生物体对毒性化合物更敏感，但在再生蠕虫中进行的三个独立实验显示，AgNP暴露对微生物组的影响不太明显，这可能是因为发育过程中潜在的细菌群落变化掩盖了AgNP诱导的作用。与未涂覆的颗粒相比，聚乙烯吡咯烷酮（PVP）涂层的存在不会显着改变实验结果。在不同实验之间观察到的变异强调了微生物组的高度可变性，并强调了在动物的生理状态之内和之间重复微生物组实验的必要性。