Interaction of lead nitrate and cadmium chloride withEscherichia coli K-12 andSalmonella typhimurium global regulatory mutants |
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Authors: | Robert A LaRossa Dana R Smulski Tina K Van Dyk |
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Institution: | (1) Environmental Biotechnology Program, Central Research and Development, DuPont Company, Experimental Statton, PO Box 80173, 19880-0173 Wilmington, DE, USA |
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Abstract: | Summary To investigate the interactions of heavy metals with cells, a minimal medium for the growth of enteric bacteria using glycerol-2-phosphate as the sole phosphorus source was developed that avoided precipitation of Pb2+ with inorganic phosphate. Using this medium, spontaneous mutants ofEscherichia coli resistant to addition of Pb(NO3)2 were isolated. Thirty-five independent mutants all conferred a low level of resistance. Disk diffusion assays on solid medium were used to survey the response ofE. coli andSalmonella typhimurium mutants altered in global regulatory networks to Pb(NO3)2) and CdCl2. Strains bearing mutations inoxyR andrpoH were the most hypersensitive to these compounds. Based upon the response of strains completely devoid of isozymes needed to inactivate reactive oxygen species, this hypersensitity to lead and cadmium is attributable to alteration in superoxide dismutase rather than catalase levels. Similar analysis of chaperonedefective mutants suggests that these metals damage proteins in vivo. |
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Keywords: | Heavy metal Resistance mutations Global regulation Oxidative damage Heat shock response |
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