Effects Of Subinhibitory Concentration Tetracycline On Changes Of Antibiotic Resistance Genes In E.coli And Microbe In Bio-ecological Wastewater Treatment System

With the increase of extensive use of various antibiotics,environmental pollution caused by the abuse of antibiotics has become more serious.The entry of low-dose antibiotics into the environment has promoted the production of antibiotic resistant genes(ARGs)in the environment,posing a great threat to human health.In order to investigate the effects of low-concentration antibiotics on the development of ARGs in the environment,our study have used Escherichia coli(E.coli)as the basic material and treated them with different subinhibitory concentrations of tetracycline for30 days to study the minimal inhibitory concentration(MIC),mutation rate and abundance of ARGs.In addition,we have also added low-dose tetracycline(19.5?g/L)to the influent of the bio-ecological wastewater treatment system,continuously monitored the system's water quality and the removal rate of antibiotics.The ARG types,abundance,and microbial community structure have been compared and analyzed before and after the addition of tetracycline.Environmental risks have been explained.The research results have been obtained as follow:(1)Continuous stimulation of antibiotics at subinhibitory concentrations can promote the development of resistance of E.coli.Under continuous exposure to low concentrations of tetracycline for 30 days,the mutation rate,MIC,species number and relative abundance of ARGs were significantly increased.The bacteria exposed to tetracycline for 30 days at a concentration of 1/32MIC(19.5?g/L)has got the highest number and relative abundance of tetracycline ARGs.(2)The bio-ecological treatment system can efficiently remove tetracycline. Cultivated plants in the experiment group have no significant effect on the degradation of tetracycline.In addition,low concentrations of tetracycline can reduce the removal efficiency of TN and NH₃-N,but have no significant effect on TP and COD.This is because tetracycline can inhibit the activity of ammonia-oxidizing bacteria in water and reduce the system's ability to remove nitrogen.(3)Tetracycline at subinhibitory concentration has no significant effect on the species number of ARGs in the bio-ecological treatment system, while it has a significant effect on relative abundance and absolute abundance of ARGs,which can weaken the system's ability to remove ARGs.However,plants can maintain the system to a certain ARG removal rate under tetracycline stress at subinhibitory concentration.(4)After the addition of tetracycline at a subinhibitory concentration,the abundance,diversity,and structure of the microbial communities in the experimental and control groups in the biological-ecological water treatment system have increased significantly.The presence of tetracycline can weaken the dominant communities,and it is the main factor leading to changes in microbial community structure.In addition, plants and dissolved oxygen content are also important factors for their species composition.In summary,the long-term existence of tetracycline at subinhibitory concentration can increase the abundance of ARGs in microorganisms,reduce the removal ability of nitrogen,affect the structure of microbial communities,and finally may cause potential environmental risks.