Rare earth oxide nanoparticles eliciting microbiota imbalance

Microbiota is crucial for maintaining the metabolic, hormonal and immunologic homeostasis of their hosts. Disruption of microbiota balance may result in severe diseases in animals and phytotoxicity in plants. While substantial concerns have been raised on engineered nanomaterial (ENM) induced hazard effects (e.g. lung inflammation), exploration of the impacts of ENMs on microbiota balance holds great implications. Here, among 19 ENMs, rare earth oxide (REO) nanoparticles were found to show severe toxicity in Gram-negative (G-) bacteria, but negligible effects in Gram-positive (G+) bacteria. This distinct cytotoxicity was related to the different molecular initiating events (MIEs) of REOs in G- and G+ strains. As a representative REOs, La2O3 was demonstrated to transform into LaPO4 on G- cell membranes and induced dephosphorylation of phospholipids, eliciting the increments of membrane fluidity and permeability. The La¬2O3-induced membrane damages G- cumulated into pulmonary microflora imbalance after exposure into mouse lungs, evidenced by a significant reduction (29.5%) of G-/G+ ratio. Besides, we disclosed a strong correlation between microflora imbalance and pulmonary inflammation.