Evolutions And Coselection Of Antibiotic And Metal Resistance Genes And Their Associationa With Bacterial Community On Microplastic Biofilms Under The Stress Of Antibiotics And Zinc

The pollution of water ecosystems by microplastics and resistance genes has been widely concerned.Microplastic specific surface may be a potential sink for potential pathogens and resistance genes,and antibiotic and heavy metal stress may exacerbate the spread of resistance genes.In this work,micro water-sediment system were used to research two common antibiotics sulfamethoxazole(SMX)and tetracycline(TC),and one heavy metal(Zn)under the effect of low,medium and high stress level,biofilms of two commonly detected microplastic polyethylene(PE)and polystyrene(PS)in the water ecosystems were incubated to investigate the evolution and coselection of antibiotic and metal resistance genes profiles and their associationa with bacterial community,further explore the potential impact of microplastics on the spread of ARGs.This research main results and conclusions are as follows:(1)16S rRNA high-throughput sequencing was used to research the evolution of bacterial communities on microplastics biofilms and their differences with natural substrate(quartz sand)under the stress of antibiotics and heavy metals.Results revealed that:the diversity of bacterial community on microplastic biofilms were higher than that on natural substrate,but there was no significant difference between them.Proteobacteria,Firmicutes and Parcubacteria shown significant differences between microplastic and natural substrate biofilms.In addition,there were significant differences in bacterial community structure under antibiotics and heavy metal were add individually or jointly(R~2=0.730,p<0.01),but no significant differences over time(R~2=0.124,p>0.05).The bacterial community structure of biofilms on two microplastics was different,and the bacterial richness of PS biofilms was significantly higher than that of PE biofilms(p<0.05).(2)according to qPCR,the total abundance of tet,MRGs and intI1 increased significantly on microplastic biofilms(p<0.01).PERMANOVA analysis showed that various antibiotics and heavy metal combinations was the dominant factor that regulated the change of the ARGs abundance(R~2=0.347-0.355,p<0.01).The abundance of ARGs under the combined stress of antibiotics and heavy metal was higher than that under the stress of single antibiotics and heavy metal,respectively,which was caused by the coselection of resistance of antibiotics and heavy metal under multiple stresses,and heavy metals play a key role in the selection of ARGs.Moreover,ARGs abundances on microplastic biofilms showed no significant difference over time(R~2=0.080,p<0.114),and there was a correlation between ARGs and bacterial community structure.There was no significant difference in the ARGs abundances of two microplastics biofilms,the intI1and ARGs abundances of PS biofilms were higher than that of PE biofilms,and the high concentration of SMX(1000?g/L)level was more conducive to increase ARGs abundances on microplastic biofilms.(3)The correlation analysis between resistance genes and bacterial community structure showed that the correlation between ARGs,MRGs and intI1 of microplastic biofilms and bacterial community was higher than that of natural substrate,and there were more potential host bacteria of ARGs on microplastic biofilms.intI1 was significantly correlated with ARGs,suggesting that horizontal gene transfer(HGT)was one of the leading mechanisms to promote the spread of ARGs in microplastic biofilms.Besides,the potential host bacteria of ARGs on biofilms of two microplastics substances were different,which may be the main reason for the difference in ARGs between the two microplastics substances.