Efficient removal for antibiotic-resistant Escherichia coli and antibiotic resistance genes from aquatic environment by BiOCl supported Ag quantum dots

Abstract

Due to the abuse and difficult removal of antibiotics, how to remove antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) in the environment is facing significant challenges. A series of efficient and non-toxic photocatalytic technologies have been proposed to solve the problem of antibiotic resistance (AR) in wastewater. However, there is limited information on changes in cell behavior and characteristics during photocatalytic processing. In this study, the prepared BiOCl loaded with silver quantum dots was used to treat ARB and ARGs in water, and the physiological characteristics of ARB after photocatalytic treatment were discussed. Using tetracycline (Tet)-resistant and ampicillin (Amp)-resistant Escherichia coli (Tet-E. coli, Amp-E. coli) as target antibiotic resistant bacteria, and using Tet-resistant genes (Tet-RGs) and Amp-resistant genes(Amp-RGs) as target resistance genes, the effects of photocatalyst dosage and silver quantum dot content on photocatalytic performance were studied under UV 365 nm irradiation. The results showed that the optimal inactivation effect was achieved by Ag QDs(500)-BiOCl at a concentration of 300 mg/L, which were 6.91 lg (tet-resistant bacteria) and 6.83 lg (amp-resistant bacteria), respectively. The plasmon resonance effect between the supported silver quantum dots and BiOCl results in the generation of free radicals dominated by holes (h+) and superoxide anions (O2•-) in the system. ARB in the system will be attacked by free radicals, and the permeability of cell membrane gradually increases. For the purpose of protection, the oxidative stress system of cells will first increase the activity of intracellular antioxidant enzymes. Due to the increase of free radicals, antioxidant enzymes gradually become inactive, ultimately leading to cell inactivation. At the same time, after photocatalytic treatment, the absolute abundance of the target resistance gene decreased by 2.79 (tetA) and 3.92 (ampC) lg. Correlation analysis found that inactivation of ARB contributes to the removal of ARGs in the system.