Study On The Selective Enrichment Of Resistance Genes And Microorganisms In Aquatic Environments By Microplastic

Microplastics and antibiotic resistance genes（ARGs）,as new environmental pollutants,pose potential risks to the environment,animal,and human health.Microplastics are ubiquitous in natural ecosystems and have become excellent carriers for ARGs and antibiotic resistant bacteria（ARB）and other bacteria in the environment.However,the impact of microplastics on the organization of the microbial community and the selective enrichment of ARGs in aquatic systems has not been investigated.Thus,it is necessary to study the selective enrichment of different types and particle sizes of microplastics on intracellular ARGs（iARGs）and extracellular ARGs（e ARGs）and microorganisms（including ARBs）in the aquatic environment.Two particle sizes（approximately 150μm and 75μm）polyvinyl chloride（PVC）,polyethylene terephthalate（PET）and polyethylene（PE）microplastics（6 microplastics samples in total）were selected as the test objects to conduct selective enrichment tests on iARGs（sul1,tet A,tet C,tet O）,e ARGs（tet A,bla TEM）and microbial communities in water respectively.The main research results are as follows:（1）Microplastics were placed in ARB sewage,and the abundances of iARGs on microplastics and in water were detected on the 5th,15th and 30th days.The results showed that microplastics can selectively enrich iARGs and int I1 in sewage.The relative abundances of tet A,sul1 and int I1 genes on all microplastics were relatively higher,while the relative abundances of tet C and tet O were at low levels.Correlation analysis showed that the relative abundances of target genes had no correlation with the particle sizes,but had a significant correlation with the material and incubation time of microplastics.Compared with PE and PVC,PET were more likely to enrich ARGs in water.（2）In order to explore the selective enrichment of e ARGs by microplastics and its influence on the natural degradation of e ARGs,microplastics were exposed to the system composed of sterile water and plasmid p WH1266 to observe the dynamic changes of absolute abundances of e ARGs on the surface of microplastics and in water.The results showed that after 30 days of incubation,the absolute abundance of e ARGs on the surface of microplastics and in water showed a dynamic change.The absolute abundances of tet A and bla _TEM genes on the surface of microplastics was 10⁶ Copies/m L and 10⁸ Copies/m L,respectively,and 10⁵Copies/m L and 10⁹ Copies/m L in water,respectively.Compared with bla _TEM,microplastics seem to adsorb tet A gene more easily.Moreover,the presence of microplastics may affect the natural degradation of e ARGs.（3）In order to observe the selective enrichment of microbial communities by microplastics with different materials and particle sizes.Different microplastics were placed in sewage for incubation experiments.On the 30th day,high throughput sequencing was performed on each microplastics and sewage sample.The results showed that the microbial diversity on the surface of microplastics was generally lower than that in water.Proteobacteria,Bacteroidetes and Firmicutes were the dominant phyla on the surface of microplastics,while Proteobacteria,Bacteroidetes and Cyanobacteria were the dominant phyla in water.Microplastics selectively enrich pathogens（Aeromonas）in water.The results of dimension reduction analysis showed that the surface of PVC,PET and PE formed unique microbial community structure.At the same time,microplastics of different materials have different effects on the shaping of bacterial community structure in water.The results of Tax4Fun function prediction show that microplastics will affect the metabolism of microorganisms in water,and may produce biological toxicity in the degradation process,which will affect the microecology of water environment in many aspects.