The Adsorption Characteristics Of Extracellular Tetracyclines Antibiotic Resistance Genes In Soil

The risk of emerging contaminants has been obtained more attention in environmental area,especially the antibiotic resistance genes.In this study,tetracyclines antibiotic resistance genes using plasmids as carriers had been considered as the targeted pollutants,and their adsorption and transformation characteristics had been analyzed by batch and column experiments.Four tetracyclines ARGs(tet B?tet M?tet O and tet W)had been detected in the recharging area of Beijing Chaobai River.The frequency of tet B was 83.3%in reclaimed water,whilst the frequency of three other ARGs in reclaimed water and soil was 100%.The abundance of tetracyclines ARGs suffered from attenuation along the river,the absolute amount of tet O was generally higher than the other three tetracyclines resistance genes.In soil samples,the abundance of genes was of high level and showed a wide fluctuation range.Compared to the control soil,the absolute abundance of genes was greater in soil samples of sediment and vadose zone which had been collected from the above recharge site.The double-room first order kinetics could well simulate the adsorption process of plasmids,which included the process of rapid adsorption and slow adsorption.The adsorption isotherms of tetracyclines ARGs plasmids were perfectly fitted by Langmuir model.The results suggested that the adsorption of plasmid vectors was much stronger in the sediment samples than the vadose zone media.The different genes fragments introduced to the plasmids showed little impacts on the adsorption capacity.In order to demonstrate the adsorption characteristics of tetracyclines ARGs,this study quantitated the absolute copy numbers of targeted genes by the method of q PCR.After the adsorption reached equilibrium,the abundance of genes decreased 1-2 orders of magnitude as compared to the initial dosage,which showed obvious adsorption effect.Simulation between the soil adsorption amount and the equilibrium concentration was performed on log-normalizedcopy numbers.It fitted the linear model well that the r2 were all above 0.99,which indicated the adsorption characteristics of tetracyclines ARGs in soil were linear adsorption within high initial abundance.Two soil columns were designed to illustrate the different constructures of the recharge site.Column I was filled with sediment and vadose zone soil with a height ratio of 1:2,whilst column II was filled with vadose zone soil.Tetracyclines ARGs had been detected at the fifth day and the second day for column I and II,respectively.The abundance of genes in column II effluent was higher than the column I.