Analysis Of Heavy Metal Tolerant Bacteria In Aquaculture Environment And Study On Their Antibiotic Degradation Performance

With the rapid development of China,the standard of living level of residents has been improved significantly.In order to meet the needs of national life,the farming industry develops quickly.Heavy metals and antibiotics,as feed additives commonly used in the farming industry,are added in large quantities,but only a small proportion of these substances are absorbed by livestock and poultry themselves,and most are released into the surrounding environment along with excrement.There is a paucity of basic data on heavy metal tolerant bacteria in the farming industry and scientific theories on the effects of heavy metal stress on the microbial degradation of antibiotics.In this thesis,based on the investigation and analysis of heavy metal tolerant bacteria in the farming environment,we conducted a study on the degradation performance of meropenem（MEM）by microorganisms under heavy metal stress to understand the mechanism of heavy metal stress on the transcriptome level of microorganisms;and verified MBL’ functional gene for hydrolysis of MEM for some strains,which provides data support for their application in environmental management.Firstly,a dilution coating method was used to investigate and analyse the number of bacteria,intestinal bacteria,and heavy metal tolerant bacteria in the farming environment.Based on the physical and chemical properties of the soil and the results of heavy metal testing,the number of different heavy metal tolerant bacteria was analysed.And the effect of different concentrations of heavy metals on the growth of bacteria was speculated to be promoted by low concentrations and inhibited by high concentrations.In this research,25 strains of heavy metal resistant bacteria were isolated and purified from different samples.14 strains of conditionally pathogenic bacteria and 11 environmentally safe strains were obtained through basic morphological observation and 16 S r DNA sequencing analysis.The transcriptome sequencing results and bioinformatics analysis showed that Cd stress could promote the high expression of some genes,for example,the MBL gene had elevated expression in the transcriptome of both strains,and MBL was further identified as a possible functional gene for hydrolysis of MEM by protein structure prediction and molecular docking techniques.Finally,heterologous expression experiments of MBL gene were conducted.By combining the MBL gene of R51 and R912 strains with the strong promoter of p MD-18 T and making the gene expressed in DH5α through transformation,the recombinant strains were all tolerant to MEM,further verifying the function of MBL gene.In conclusion,this research provides data to supplement the current status of heavy metal tolerant bacteria in the farming environment,and proposes a novel treatment method for antibiotic and heavy metal pollution,and provides a theoretical basis for the application of MBL gene in environmental treatment.