Comparative toxicity assessment of CeO2 and ZnO nanoparticles towards Sinorhizobium meliloti, a symbiotic alfalfa associated bacterium: Use of advanced microscopic and spectroscopic techniques

► First cytotoxicity study of CeO2 and ZnO nanoparticles to Sinorhizobium meliloti. ► First report upon the mechanisms of CeO2 and ZnO NPs toxicity to S. meliloti. ► ZnO NPs were found to be bactericidal in lower concentration. ► CeO2 NPs had bacteriostatic effect on S. meliloti.