The presence of high-molecular weight proteins with a strong affinity for cadmium in environmental Escherichia coli strains.

High molecular weight proteins, with a strong affinity for cadmium, were found in two environmental strains of Escherichia coli isolated from a wastewater treatment plant and were resistant up to 128 ppm of Cd+2. The fraction containing intracellular cadmium binding proteins was obtained by affinity chromatography and the single components of the same fraction were separated by SDS-gel electrophoresis in order to calculate molecular weights ranging from 48 to 89 kD. Plasmid analysis, carried out by agarose gel electrophoresis, and transformation experiments demonstrated that the plasmids, isolated from one of the strains which was resistant to tetracycline and streptomycin, are not related to the synthesis of cadmium-binding proteins.