Occurrence And Abundance Of Antibiotic Resistance Genes In Biofilms On Plastics In Yangtze Estuary

As we known,plastic pollution is of great concern in recent years,and it can serve as a possible vector for the spread of antibiotics resistance genes(ARGs).ARGs and plastic wastes are widely found in the aquatic environment,moreover,the biofilm formed on the plastics surface will contain a variety of pollutants,including ARGs.However,the types and contents of these ARGs and their environmental influencing factors remain to be studied.Therefore,this study focused on the occurrence and distribution of ARGs,MRGs and their associated microbial communities in biofilms formed on different types of plastics,in comparison to associated sediment and water samples taken from the Yangtze Estuary.In addition,we incubated biofilm on different types of plastic samples in natural water environment for 30 days,in order to investigate the relationship between the occurrence of ARGs in biofilms and plastic types.Based on the above research,the main conclusions of this study are as follows:(1)Plastic wastes with visible biofilms were widely existing in the intertidal environments along the Yangtze Estuary,especially for polypropylene(PP)and polyethylene(PE).The average abundances of most ARGs on plastics were higher than those in sediment and water,indicating that biofilms on plastics can act as a reservoir for ARGs in the Yangtze Estuary.Moreover,the abundance of ARGs at XP,QYK and LHK were generally higher than those at SDK,WSK,SCK,CY and LCG.(2)The positive significant correlations were found between int I1 and several ARGs in biofilms on plastics,indicating int I1 may participate in the occurrence and propagation of ARGs in biofilms on plastics.According to the results of the PCA and the ANOSIM test,plastic types maybe not the dominant factor that regulated the distribution of absolute ARGs abundance in the Yangtze Estuary,and the biofilms on PE have a high relative abundance of ARGs which suggested PE have high risk for ARGs.(3)The biofilm metal concentrations and estuarine salinity had significant correlation to most of ARGs,and they may regulate the occurrence and distribution of ARGs in biofilms on plastics.For example,several metals showed significant correlation to sul1,sul2,tetW and acc(6')-Ib and cop A may co-exist with ARGs in biofilms on plastics.Moreover,salinity was a vital factor to regulate the distribution of ARGs in biofilms,and other environmental including TOC,pH,DO,and TN had few significant correlations to ARGs on plastics taken along the Yangtze Estuary.(4)Most ARGs were correlated with MGEs and MRGs(P < 0.01)in biofilm on different types of plastic at SDK.In particular,sulfonamides resistance gene sul1,tetracyclines resistance gene tet A and fluotoquinolones resistance gene qnrS were significantly positively correlated with MGEs and MRGs(P < 0.001),indicating that the MGEs and MRGs are also the main environmental factors affecting the ARGs,and to some extent,they may accelerate the spread of ARGs in biofilms in the environment.(5)Through the analysis of the composition and structure of the bacterial communities in biofilm on different types of plastic at SDK,it was found that the bacterial community is dominated by Proteobacteria,Bacteroidetes and Acidobacteria,and there are synergistic and antagonistic effects between the bacterial community and most ARGs.(6)When different types of plastic samples were cultured in biofilms in natural water environment for 30 days,PE plastic was more likely to enrich ARGs,which may be related to the slight differences in physical and chemical factors such as the hardness of different types of plastic surfaces...