Engineering a mouse metallothionein on the cell surface of Ralstonia eutropha CH34 for immobilization of heavy metals in soil

Here we describe targeting of the mouse metallothionein 1 (MT) protein to t he cell surface of the heavy metal-tolerant Ralstonia eutropha (formerly Al caligenes eutrophus) CH34 strain, which is adapted to thrive in soils highl y polluted with metal ions. DNA sequences encoding MT were fused to the aut otrans-porter beta-domain of the IgA protease of Neisseria gonorrhoeae, whi ch targeted the hybrid protein toward the bacterial outer membrane. The tra nslocation, surface display, and functionality of the chimeric MT beta prot ein was initially demonstrated in Escherichia coli before the transfer of i ts encoding gene (mtb) to R. eutropha. The resulting bacterial strain, name d R. eutropha MTB, was found to have an enhanced ability for immobilizing C d2+ ions from the external media. Furthermore, the inoculation of Cd2+-poll uted soil with R. eutropha MTB decreased significantly the toxic effects of the heavy metal on the growth of tobacco plants (Nicotiana bentamiana).