Impact of CeO2 nanoparticles on the microbiota of the S. flos-cuculi L. (Caryophyllaceae) rhizosphere†

The aim of this study was to correlate the influence of cerium oxide nanoparticles (nCeO₂) resulting from pollution sources, on the root bacterial composition and the associated substrate (root zone soil) of Silene flos-cuculi (L.) using a metabarcoding technique. Currently, limited information is available regarding the direct effects of nCeO₂ on plants and the rhizosphere microbiota, where changes in turn could positively or negatively influence plant performance. To assess the distribution of the main bacterial phyla in the culture substrates, analyses were conducted considering both intracellular DNA (iDNA) contained within intact and live bacterial cells, and extracellular DNA (eDNA) from lysed cells. The impact of various nCeO₂ dosages on phyla, families, and genera was then investigated with a detailed examination of all detected members at the family and genus levels to differentiate the nCeO₂ treatment effects. The results revealed that 25 out of 641 identified bacterial genera, primarily anaerobic and strictly anaerobic, exhibited reduced presence in nCeO₂ treated samples compared to the controls. This decrease was particularly evident in species belonging to the phylum Firmicutes. Metabolic function analysis performed using FAPROTAX indicated a decline in fermentative, nitrogen fixation, and iron/nitrate respiration metabolisms in nCeO₂ treated samples, especially at higher concentrations. Conversely, there was an increase in chemo-heterotrophy and aerobic chemoheterotrophic-related functions in these samples.