| In this study,the interaction between the change of ARGs and the expression of microcystins synthase gene in the synthetic wastewater containing Graphene oxide(GO)with gradient concentration was investigated.The results demonstrated that when the GO concentration was 0.01 mg/L,the absolute abundance of sull,sul2,tetW and tetM in the synthetic wastewater increased significantly to 365.2%,427.1%,375.2%and 231.7%,respectively.The total gene copy number of the microcystins synthase gene cluster mcyA-J was also increased to 243.2%.The occurrence of GO resulted in a significant correlation between the abundance of ARGs and the expression of mcyA-J.In addition,at 0.01 mg/L GO,Microcystis aeruginosa(M.aeruginosa)exhibited better photosynthetic performance and produced more microcystis(MCs).There were 65 pairs of positive correlations between the different metabolites in algal cells of M.aeruginosa and the abundances of sull,sul2,tetM and tetW in the samples under different GO concentrations.The presence of GO will affect the relative abundance of metabolites and the changes of metabolic pathways in M.aeruginosa.The changes of intracellular metabolites in algal cell affected the changes of ARGs abundance,microcystins synthase gene and other physiological characteristics.There were complex correlations among ARGs of sull,sul2,tetM,tetW,mcyA-J,MCs,photosynthetic performance and ROS.Some concentrations of GO will promote the expression of mcyA-J and produce more MCs,thus aggravating the harm of M.aeruginosa,and may also cause the diffusion of ARGs.On the basis of the above results,the natural water was used to explore the influence of carbon based copper nanocomposites on the horizontal transfer of antibiotic resistance genes(ARGs)and the removal of M.aeruginosa.The water samples in this study were collected from the water system of Haihai Town,Fengxian District,Shanghai.The in-situ high-throughput microbial diversity,concentration of chlorophyll a,living/dead ratio of M.aeruginosa,zeta potential,and metagenomic characters were detected.The results demonstrated that the appropriate concentration of carbon-based nano-copper composite material can effectively promote the flocculation of M.aeruginosa in natural water,and the ratio of dead cells to live cells in the system increased significantly.The presence of the composite material did not destroy the in-situ microbial diversity in the natural water.The relative abundance of Cyanobacteria and M.aeruginosa in natural water can be effectively reduced by 20 mg/L carbon nanocomposites.20 mg/L carbon nanocopper composites material significantly reduced the abundance of ARGs of sull,sul2,tetM were the most obvious decreased.Most of the ACCs(ARG-carrying contigs)in the samples were located in the plasmids,and the proportion of ACCs in the plasmids was significantly reduced when the concentration of carbon nanocopper composite was 20 mg/L.The presence of 20 mg/L carbon nanocopper composite significantly(P<0.05)reduced the co-occurrence of ARGs and MGEs(MGEs)mobile genetic elements,and to some extent reduced the potential spread of ARGs by horizontal transfer mediated by plasmids and integrative conjugating elements.The coverage of ARGs on the plasmid was significantly decreased(22.7%)when the concentration of carbon nanocopper composites was 20 mg/L.Pearson correlation analysis shown that the number of potential hosts of sull and sul2 was significantly reduced when the concentration of carbon nanocopper composites was 20 mg/L.These results will provide some useful reference for the removal of M.aeruginosa and the horizontal transfer control of ARGs in natural water. |
