Monitoring the developmental impact of copper and silver nanoparticle exposure in Drosophila and their microbiomes.

There is concern that waste waters containing manufactured metal nanoparticles (NPs) originating from consumer goods, will find their way into streams and larger water bodies. Aquatic invertebrates could be vulnerable to such pollution, and here we have used fruit flies, Drosophila melanogaster, as a model invertebrate, to test for the effect of NPs on fitness. Both copper NP and microparticle (MP)-containing medium slowed development, reduced adult longevity and decreased sperm competition. In contrast, ingestion of silver resulted in a significant reduction in developmental success only if the metal particles were nanosized. Ag NP-treatments resulted in reduced developmental success as assessed by larval and pupal survival as well as larval climbing ability, but there was no impact of silver on adult longevity and little effect on reproductive success. However, Cu NPs generally appeared to be no more toxic to this invertebrate model than the bulk counterpart. The impact of silver ingestion in larvae was further investigated by 454 pyrosequencing of the 16S rRNA genes of the midgut flora. There was a striking reduction in the diversity of the gut microbiota of Ag NP-treated larvae with a rise in the predominance of Lactobacillus brevis and a decrease in Acetobacter compared to control or Ag MP-treatment groups. Importantly, these experiments show that perturbation of the microbial assemblage within a metazoan model may contribute to Ag NP-mediated toxicity. These observations have implications for impact assessments of nanoparticles as emerging contaminants.