Construction and characterization of an Escherichia coli strain genetically engineered for Ni(II) bioaccumulation

An Escherichia coli strain that accumulated Ni(II) was constructed by intro ducing the nixA gene (coding for a nickel transport system) from Helicobact er pylori into JM109 cells that expressed a glutathione S-transferase-pea m etallothionein fusion protein. The resulting strain accumulated 15 mu mol o f Ni(II) per g (dry weight) from a 10 muM NI(II) solution, four times the l evel taken up by JM109 cells. NI(II) accumulation did not require an energy source, was inhibited by only 50% by 0.1 M NaCl, and occurred over the pH range from 3 to 9.