Cadmium transport by a Cd2+-sensitive and a Cd2+-resistant strain of Bacillus subtilis

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Abstract
Cadmium uptake by a Cd2+-sensitive (1A1) and a Cd2+-resistant mutant (1A1r) strain of Bacillus subtilis was investigated. Uptake of 109Cd2+ was determined for cells of both strains grown in tryptone broth and in broth containing tryptone, yeast extract, and glucose (TYG). The extent of 109Cd2+ uptake by cells of 1A1r was less than by cells of 1A1 under both growth conditions. In both growth media, 109Cd2+ uptake by 1A1 cells demonstrated saturation kinetics and was energy dependent. In both TYG and tryptone broth, 109Cd2+ uptake by 1A1 cells was inhibited by the addition of unlabeled Mn2+. Although lower in magnitude, the kinetics of 109Cd2+ uptake by 1A1r cells were similar to those of 1A1 cells when grown in tryptone broth. However, no obvious saturation kinetics, energy dependence, temperature sensitivity, or inhibition of 109Cd2+ uptake by the addition of unlabeled Mn2+ was observed in 1A1r cells grown in TYG. Differential Mn2+ accumulation by 1A1r cells in TYG and tryptone broth correlated with differential 109Cd2+ uptake by 1A1r cells in these media.