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

Abstract

Environmental nanoparticles (NPs) and microbes are integral parts of natural ecosystems, and they interact inevitably in aquatic environments. However, most previous studies mainly focused on engineered 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 growth, cell activity, intracellular reactive oxygen species (ROS), and oxidative stress responses in E. coli. Then, the contribution of metal species in the key component of environmental NPs to bacterial oxidative stress was also investigated. Results showed that the environmental NPs could significantly inhibit bacterial growth (25.74–40.35%) and increase intracellular adenosine-triphosphate (ATP) (27.69–62.83%), ROS (2.57–20.72%), and activities of superoxide dismutase (SOD) (65.93–106.33%) and catalase (CAT) (795.47–1600.95%) within 24 h of exposure. Further, the intact morphology of bacterial cells was destroyed, and mRNA levels of oxidative stress, membrane protein, and cell repair genes were 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 Fe, Si, and Zn) in environmental NPs contributed the most to bacterial oxidative stress. Further speciation analysis indicates that the Al species was dominated mainly γ-Al₂O₃. This study provides new insight into the underlying mechanisms and links between environmental NP structure and bacterial oxidative stress in real environmental systems.