This study was focused on the application of electrochemical methods for studying of bacterial strains Escherichia coli and Escherichia coli expressing human metallothionein gene (MT-3) before and after the application of cadmium and/or lead ions in four concentrations (25, 50, 75 and 150 mu M). Bacterial strains Escherichia coli and Escherichia coli expressing human metallothionein gene (MT-3) were used like model organisms for studying of metals influence to metallothionein expression. Metallothionein was isolated using fast protein liquid chromatography and quantified by electrochemical methods. The occurrence of metallothionein in E.coli was confirmed by gel electrophoresis by the presence of the bands at 15 (MT dimer) and 22 kDa (MT trimer). The changes in electrochemical records due to the interactions of metallothioneins (MT-3 and MT-2A) with cadmium and lead ions showed decline of Cat2 signal of MT with the increasing interaction time because of metal ions binding to cysteines. Electrochemical determination also revealed that Cd(II) remains in E. coli cells in the higher amount than Pb (II). Opposite situation was found at E. coli-MT-3 strain. The antimicrobial effect of cadmium ions was determined by IC50 and was statistically calculated as 39.2 and 95.5 mu M for E. coli without cloned MT-3 and E. coli carrying MT-3 gene, respectively. High provided concentration IC50 in strains after lead ions application (352.5 mu M for E. coli without cloning and 207.0 mu M for E. coli carrying cloned MT-3 gene) indicates lower toxicity of lead ions on bacterial strains compared to the cadmium ions. (C) 2014 Elsevier Ltd. All rights reserved.