The Antibacterial Mechanism Of CuO ENPs In The Presence Of DOM

With the development of nanotechnology, nanomaterials were used in medicine, cosmetics, paints, dyes, optoelectronic device, water treatment, air purification. The usage, transport, disposal of nanomaterials will lead them into environment with atmospheric sedimentation, surface runoff, underground leakage, especially water environment. Many studies had proved the nanoparticles (ENPs) could contact with animals, microbes, plants, accumulate in the organisms and finally lead to the toxicity. Microbes are the basic decomposer, in the bottom of the food chain, widely used in food, medicine, water purification. The study of the toxicity of ENPs to bacteria would supply theory for eukaryote. Till now, most of the studies about the toxicity of ENPs to bacteria are investigated in the dissolved water in the lab environment. Whereas, the aggregation and adsorption behavior properties of ENPs may change because of the complex hydrochemistry condition of natural water such as pH, ironic strength, dissolved organic matter (DOM). And then the toxicity behavior of ENPs to bacteria will change. The objective of this study is to find out the toxicity mechanism of ENPs in the natural water and the role of DOM antibacterial mechanism in the natural water.The hydraulic radius of CuO ENPs was lower than bulk CuO particles, but the surface area was larger than them. SRFA increased the electronegativity and hydraulic radius of CuO ENPs. SRFA adsorbed onto the surface of CuO ENPs.CuO ENPs (10 nm) in the MD medium made by dissolved water significantly inhibited the growth of bacteria, with the inhibition rate of 49.95% at 2 h, which significantly higher than bulk CuO (1.5μm). And the inhibition rate showed time and concentration dependent. So, at 2 h 10 mg L^-1 CuO ENPs chose as the next mechanism experiment condition.The membrane of CuO ENPs treatment was incomplete under TEM and SEM images. Because of the randomness of TEM and SEM, the membrane of the cells was further investigated by laser confocal fluorescence microscopy and flow cytometry. And the results showed CuO ENPs destroyed the membrane. K⁺ as the indicator of membrane stability was determined. CuO ENPs lead to the efflux of K⁺. Meanwhile, CuO ENPs entered into the cells which would influence the physiological metabolism of the bacteria. CuO ENPs made the protein concentration decrease and DNA concentration increase. There was no oxidative damage under the CuO ENPs treatment.The inhibition rate of CuO ENPs in the natural water was slightly decreased. SRFA as a model DOM was used to investigate the role of DOM in the toxicity mechanism of CuO ENPs to bacteria in the natural water. The inhibition rate was decreased in the presence of SRFA. The membrane became compact by SEM images and the toxicity was mitigated in the presence of SRFA. The concentration of K⁺ was descended when added SRFA in the dissolved water MD medium. SRFA adsorbed onto the surface of ENPs and bacteria decreased the contact of ENPs and bacteria, mitigated the toxicity of membrane, and then decreased the toxicity of ENPs to bacteria.