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 culture medium of Acidiphilium sp. markedly increased Co2+, -resistance of the cells. The mechanism of Co2+-resistance was studied with Acidiphilium sp.35. Cobaltous ion (50 mM) inhibited uptake of14C-glucose into intact cells and the acitivity of glucose oxidation. The activity of glucose oxidation was restored by adding ferrous or ferric ions (4 mM) in the reaction mixture, but14C-glucose uptake activity was not. Ferrous or ferric ions strongly 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 Co2+ -resistance by those ions.