Lighting E. coli cells as biological sensors for Cd2+

Whole cells of E. coli expressing a chimeric cadmium-binding peptide fused to green fluorescent protein (CdBP-GFP) were prepared and applied for the determination of cadmium. Construction of the structural gene was performed by inserting two synthetic oligonucleotides coding for four repeats of a Cd-binding peptide (His-Ser-Gln-Lys-Val-Phe) into the 5-end of the GFPuv gene. Similarly, a hexahistidine-green fluorescent protein (his₆GFPuv) was prepared and used as a reference in the determinations of heavy metals. The lowest concentrations of Cd, which activated the fluorescence, were 0.5 M, 50 M, and 0.5 mM for cells carrying CdBP₄GFP, his₆GFP and native GFP, respectively.