Key component group of environment nanoparticles and corresponding contribution to oxidative stress of Escherichia coli in water

Abstract

Environmental nanoparticles (NPs) and microbes are integral parts of natural environments, and they interact inevitably in water environments. However, most previous studies mainly focused on engineering NPs, and the effects and key components of environmental NPs on microorganisms have not been fully clarified. Herein, we collected the environmental NPs from an estuary to study their corresponding effects on E. coli growth, cell activity, intracellular reactive oxygen species (ROS), oxidative stress responses in E. coli. Then, contribution of metal species in key component of environmental NPs to bacterial oxidative stress was also investigated. Results showed that the environmental NPs could significantly inhibit the bacterial growth (25.74%–40.35%) and increase the intracellular adenosine-triphosphate (ATP) (27.69%–62.83%), ROS (2.57%–20.72%), the activities of superoxide dismutase (SOD) (65.93%–106.33%) and catalase (CAT) (795.47%–1600.95%) within 24 h of exposure. Further, intact morphology of bacterial cells was destroyed, and mRNA levels of oxidative stress, membrane protein, and cell repair genes upregulated. Asymmetrical flow field flow fraction (AF4) combined with multiple linear regression analysis showed that the largest size component (843.83 nm) and Al species (followed by Si, Fe, Zn) in environmental NPs contributed the most to bacterial oxidative stress. Further metal species characterization indicates that the Al species was dominated mainly γ-Al2O3. This study provides new insight into the underlying mechanisms and links between environmental NPs structure and bacterial oxidative stress in the real environmental system.