Alterations induced by transition metals nickel, cadmium and mercury in Salmonella typhimurium growth and membrane proteins

摘要

Salmonella typhimurium was cultured either in minimal or in enriched medium in the presence of increasing concentrations of Ni~(2+), Cd~(2+), Hg~(2+) and exhibited a much higher sensitivity to Hg~(2+) than to the other two metal ions. After 24 h growth in minimal medium the yield decreased by 50% in the presence of 0.26 mM Ni~(2+) and by 60% in the presence of either 0.08 mM Cd~(2+) or 0.0008 mM Hg~(2+). After growth in enriched medium, the yield decreased by 80% in the presence of 15 mM Ni~(2+) or 5 mM Cd~(2+) and by 65% in the presence of 0.03 mM Hg~(2+). Cytochromes were used as a probe to investigate the effect of metals on membrane proteins. Increasing metal concentrations led to increasing reductions in the amount of all cytochromes (b560, b595 and d) although to various extends, depending on the metal and on the cytochrome. At metal concentrations that drastically diminished the cell yield, cytochrome b595 was the most affected in the presence of Ni~(2+) or Cd~(2+), while cytochrome d was the most affected in the presence of Hg~(2+). Results indicated that Hg~(2+) distinguished itself from Cd~(2+) and Ni~(2+) by the concentration range tolerated by the bacterium as well as by the effect observed on the cytochromes.