Ni2+ -uptake in Pseudomonas putida strain S4: a possible role of Mg2+-uptake pump

摘要

Essential metal ion homeostasis is based on regulated uptake of metal ions, both during its scarcity and abundance. Pseudomonas putida strain S4, a multimetal resistant bacterium, was employed to investigate Ni 2+ entry into cells. It was observed that Mg 2+ regulates the entry of Ni 2+ and by this plays a protective role to minimize Ni 2+ toxicity in this strain. This protection was evident in both growth as well as viability. Intracellular accumulation of Ni 2+ varied in accordance with Mg 2+ concentrations in the medium. It was hypothesized that Ni 2+ enters the cell using a broad Mg 2+ pump, i.e. the CorA system, as the CorA inhibitor, i.e. Co(III) Hex, also inhibits Ni 2+ uptake. This led to the inference that Mg 2+ -based protection was basically due to competitive inhibition of Ni 2+ uptake. We also show that Zn 2+ can further regulate the entry of Ni 2+.