Combined Engineered Microbes And Alfalfa Bioremediation Of Cadmium And Nickel Pollution Based On Display Technology

Heavy metal pollution is one of the world’s widespread problem. At present, bioremediation is considered the most vital environmental remediation technology because it is economic and without secondary pollution. Phytoremediation of heavy metals in the environment is the most studied and most promising method. Microbial remediation is another promising technology. Currently, the focus and difficulty of the research is to obtain high affinity and specificity metal-binding peptides and finding of microbes with heavy metal resistance or heavy metal tolerance and thriving under different environmental conditions. By using the mutually symbiotic relationship between plants and microorganisms, the microbes and plants combined remediation technology would be expected to be more efficient in the bioremediation of heavy metal pollutions.In this study, we displayed heavy metal-binding peptides on the surface of bacteria on the basis of our preliminary studies of the phage peptide library screening. Agarose gel electrophoresis, Western and ELISA, etc identified that heavy metals binding peptides had been successfully displayed on the surface of E. coli. Tolerance and adsorption test of Cd by these engineered bacteria showed that the heavy metal binding peptides engineered bacteria significantly improved the tolerance of Cd. The results are as follows:XL1-Blue-MBP1> XL1-Blue-MBP2> E.coil-HAGS> XL1-Blue, the tolerant of recombinant wild E.coli for heavy metal are as follows:Wild-MBP1> Wild-MBP2> Wild-HAGS> Wild E.coli> Wild-His. Except for XL1-Blue-MBP1, the adsorption of heavy metals for recombinant laboratory srains were not satisfactory. Contrary, the recombinant wild E.coli were obviously more effective on the adsorption of heavy metals, the results are as follows Wild-His>Wild-MBP1>Wild-MBP2>Wild E.coil> Wild-HAGS. In order to find if the Cd heavy metal-binding peptides would also be effective for other heavy metals, Ni heavy metal adsorption were also tested, the results were similar and confirmed that the Cd heavy metal binding peptides had a a broad spectrum of adsorption for Cd and Ni heavy metals. Finally, we tested the engineered bacteria and alfalfa combined treatment of heavy metal. The results showed that engineered bacteria which displayed heavy metal binding peptides not only had a strong heavy metal repair capacity but also improved the uptake of alfalfa for heavy metals, the results are as follows:Wild-His, Wild-MBP1Wild-MBP2, Wild E.coil, Wild-HAGS.In order to study the adsorption of heavy metals of heavy metals binding peptide in eukaryotes such as yeast, MBP1was also displayed on Saccharomyces cerevisiae EBY100. The results showed that the recombinant yeast also had a strong heavy metal adsorption capacity.