Improvement of Co²⁺-resistance of genus Acidiphilium on the presence of iron-ion

Strains of Acidiphilium sp. resistant to four heavy metals such as 10 mM Co²⁺, 100 mM Ni²⁺, 10 mM Cd²⁺ and 0.01 mM Hg²⁺ were obtained. An addition of ferrous or ferric ions in the culture medium of Acidiphilium sp. increased Co⁺² resistance of the cells. The mechanism of Co²⁺ resistance was studied. Cobaltous ion (50 mM) inhibited uptake of ¹⁴C-glucose into intact cells and the activity of glucose oxidation. The activity of glucose oxidation was restored by adding ferrous or ferric ions (4 mM) in the reaction mixture, but ¹⁴C-glucose uptake activity was not restored. Ferrous or ferric ions inhibited an accumulation of Co²⁺ in the strain, suggesting that inhibition of Co²⁺ uptake by ferrous and ferric ions is responsible for the improvement of Co⁺² resistance by those ions.