Engineered ZnO and TiO2 nanoparticles induce oxidative stress and DNA damage leading to reduced viability of Escherichia coli

► Flow cytometry and TEM revealed an internalization of ZnO and TiO2 ENPs in E. coli. ► ZnO and TiO2 ENP exposure increased ROS generation. ► ROS induction resulted in DNA and membrane damage leading to cell death. ► Our data suggest a possible mechanism of ENP induced toxicity in bacteria. ► The study reiterates the need for environmental risk assessment of commercial ENPs.