Background: A bacterial biosensor refers to genetically engineered bacteria that produce an assessable signal in the presence of a physical or chemical agent in the environment. Methods: We have designed and evaluated a bacterial biosensor expressing a luciferase-reporter gene controlled by pbr and cadA promoters in Cupriavidus metallidurans (previously termed Ralstonia metallidurans) containing the CH34 and pI258 plasmids of Staphylococcus aureus, respectively, and that can be used for the

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... ction of heavy metals. In the present study, we have produced and evaluated biosensor plasmids designated pGL3-luc/pbr-biosensor and pGL3-luc/cad-biosensor, that were based on the expression of luc+ under the control of the cad promoter and the cadC gene of S. aureus plasmid pI258 and pbr promoter and pbrR gene from plasmid pMOL30 of Cupriavidus metallidurans. Results: We found that the biodegradable pGL3-luc/pbr-biosensor could be used to measure lead concentrations between 1-100 μM in the presence of other metals, including: zinc, cadmium, tin and nickel. The latter metals did not result in any significant gene expression of the reporter. The pGL3-luc/cad-biosensor was able to detect lead concentrations between 10 nM to 10 μM. Conclusions: This biosensor was found to be a specific for measuring lead ions in both environmental and biological samples.