The Distribution Characteristic And Mechanism Of Antibiotic Resistome Between Dyeing And Domestic Wastewater

The spread of antibiotic resistance genes(ARGs)have been identified as a global environmental problem,domestic wastewater treatment plants has always been the hot research spot as the ARGs reservoir,but dyeing wastewater,with large discharge volume,high concentration of organic matter and complicated composition,microorganism toxicity,has not received enough attention.Dyeing wastewater contains bulk of benzenes,PAHs,quaternary ammonium compound,which are poisonous to bacteria,and possibly promoting the emergence and propagation of ARGs.Therefore it's essential to study the fate of ARGs in dyeing wastewater.In this study,we aimed to investigate the differences in distribution of ARGs and microbial communities between mixed(dyeing and domestic)wastewater and domestic sewage from the same district,using high-throughput quantitative PCR and 16S rRNA gene sequencing.Conjugation transfer experiment was performed to analyze the effect of dyeing wastewater on horizontal genes transfer,and explore the mechanism of ARGs transferring during dyeing wastewater treatment.The total absolute abundances of ARGs in inflows and excess sludge samples has no obvious fluctuations seasonally,while those in outflow samples in winter fell comparing with inflow samples.LEfSe analysis showed there were 11 kinds of high ARGs abundance in summer samples(aadA5-02,aac-6-?,cm1A1-01,cm1A1-02,blaOXA10-02,aadA-02,tetX,aadA1,ereA;qacE?1-01,blaTEM)and 10 kinds of high ARGs abundance in winter samples(tet-32,tetA-02,aacC2,vanC-03,aac-6-I1,tetE,ermB,mefA,tnpA-07,sul2).The relative abundance of bacteria at phylum level has no significant seasonal changes.On the family(or genera)level,the dominant bacteria in summer are Synechococcus and vadinCA02 and those in winter are Trichococcus,Lactococcus,Pelosinus,Janthinobacterium,Nitrosomonadaceae and Sterolibacterium.The dominant bacteria have good correlation with high abundance ARGs in the same season.In conclusion,bacterial changes drive the different distribution of ARGs during the seasonal change.The normalized copy numbers of ARGs in mixed wastewater were higher than those in domestic wastewater.The relative abundance of mobile genetic elements(MGEs)in inflow of dyeing wastewater was 3.7-13.1 times higher than that in other samples.Spearman correlation between MGEs and ARGs was significant(R=0.933,p=0.001),meanwhile the aminoglycoside resistant genes correlated significantly with MGEs(R=0,800,p=0.010).Ttreatment process had poor effect on the removal of MGEs,which belonged to the persistent genes.Therefore,abundant MGEs existing in dyeing wastewater is the main reason for higher ARGs abundance in mixed wastewater than that in domestic sewage.The bacterial community structure in dyeing wastewater didn't change obviously during water treatment process.Firmicutes closely correlated with high-abundant ARGs(acrR-01,acrB-01,rarD-03,blaSHV-01,blaSHV,02,bacA-02,ampC-07)in dyeing wastewater especially for Streptococcus in Firmicutes,which was the most prevalent predicted genus of these ARGs.The results of conjugation transfer show that malachite green,trioxymethylene,ethylbenzene,o-xylene,styrene and 2,4-dichloroaniline all facilitated the transfer of resistance-carrying RP4 plasmid and the highest transfer frequency(about 10-5-10-3)was over 4-200 fold higher than that in the control group(about 10-6-10-5).These results illustrated that six common residual compounds especially low-dose substances in IDW3 could facilitate the dissemination of ARGs in the water environment.