The Impact of Nanoparticles and Molecular Forms of TiO2 on the Rhizosphere of Plants in the Example of Common Wheat (Triticum aestivum L.) – Shifts in Microbiome Structure and Predicted Microbial Metabolic Functions

This study investigated the effects of various titanium nanoparticles (TiO2NPs) on the structure, function, and trophic levels of the wheat rhizobiome. In contrast to the typically toxic effects of small nanoparticles (~10 nm), this research focused on molecular TiO2 and larger nanoparticles: medium-sized (68 nm, NPs1) and large (>100 nm, NPs2). The results demonstrated significant yet diverse impacts of different TiO2 forms on the rhizosphere microbiota. Large TiO2NPs2 and mo-lecular TiO2 adversely affected the bacteriobiome and mycobiome, leading to an increase in au-totrophic microbial groups. In contrast, medium-sized TiO2NPs1 shifted the microbiome toward chemoheterotrophy, promoting plant growth–associated bacteria, fungal saprotrophs, and po-tential phytopathogens, suggesting a beneficial r-strategy within the rhizosphere. Other treat-ments induced oligotrophic conditions, resulting in a less flexible rhizobiome with diminished root associations but an increased abundance of Trichoderma spp. Structural modeling revealed that even minor changes in operational taxonomic units (OTUs) could significantly alter the micro-biota's metabolic potential. These findings highlight the importance of further research to opti-mize nanoparticle applications for sustainable agriculture.