Growth and adaptation of Saccharomyces cerevisiae at different cadmium concentrations

The effect of 0, 5, 10 and 25 mg l-1 cadmium on the growth of Saccharomyces cerevisiae in defined medium has been investigated. It was found that the length of the lag phase increased with cadmium concentration and that metal uptake during the lag phase occurred only at a cadmium concentration of 25 mg l-1. However, metal uptake occurred at all cadmium concentrations during the exponential phase. The yeast was gradually adapted to cadmium by a series of subcultures which resulted in a decrease in the length of the lag phase. Adaptation also caused a reduction in the cadmium uptake during the lag phase at 25 mg l-1 cadmium but did not affect uptake during the exponential phase at any concentration. A single passage through cadmium-free medium partially reversed the adaptation process. Sulphide production was enhanced significantly when the yeast was grown in the presence of increasing cadmium concentrations. However, at 5 mg l-1 cadmium, adapted cells produced less sulphide than unadapted cells, whilst at 10 and 25 mg l-1 cadmium the production of sulphide was similar for adapted and unadapted cells.