Impact of titanium dioxide nanoparticles on the soil microbiome

Titanium dioxide nanoparticles (TiO2 NPs) are the most produced NPs worldwide and have great potential to be utilized in agriculture as additives for plant protection products. However, concerns have been raised that some NPs may negatively affect crops and soil microbial communities, including beneficial microbes such as arbuscular mycorrhizal fungi. Here we tested two different TiO2 NPs (P25, E171) and a bulk TiO2 (particle size >100 nm) for their effects on the diversity and community composition of soil microorganisms. In addition we tested whether increasing concentrations of TiO2 NPs had effects on wheat growth and yield. Microbial diversity was analyzed using Illumina Miseq paired-end sequencing of ribosomal markers (prokaryotic 16SV3V4 and eukaryotic ITS2 of the rrn operon). Application of TiO2 NPs altered the detected prokaryotic but not micro-eukaryotic community structure. No negative effects on wheat growth and on arbuscular mycorrhizal root colonization were detected, and no evidence for a dose-response relationship between wheat performance and TiO2 NP concentration was found. Overall, these results reveal that prokaryotes were more sensitive than eukaryotes to the TiO2 NP treatments, which might potentially be based on NP interaction with their different surface structures, e.g., murein (bacteria) and chitin (fungi).