Accumulation and transport of cadmium by tolerant and susceptible strains of Mycobacterium scrofulaceum.

Cadmium accumulation and transport were studied in two strains of Mycobacterium scrofulaceum differing in their susceptibility to Cd2+ toxicity. A 10-fold excess of either Zn2+ or Mn2+ partially antagonized inhibition of growth by Cd2+. 109Cd2+ uptake by both the tolerant and susceptible strains was temperature dependent and inhibited by a 10-fold excess of either Zn2+ or Mn2+. There were no significant differences in either the kinetics of 109Cd2+ uptake or the retention of accumulated 109Cd2+ by the tolerant and susceptible strains. Both tolerant and susceptible strains removed most of the cadmium from the culture medium, but significantly more was removed by cells of the tolerant strain. Most of the accumulated Cd2+ in the tolerant strain was in the particulate fraction, rather than in the soluble fraction. Intracellular accumulated Cd2+ was primarily in the soluble fraction of the susceptible strain. Increased Cd2+ in culture medium resulted in decreased Mn2+ and Zn2+ in cells of the susceptible strain but did not reduce the Mn2+ and Zn2+ content of cells of the tolerant strain.