A bacterial biosensor is reported that responds to Pb2+ in the range of 50-400 μM by expressing green fluorescence protein (GFP). The genetic element that senses Pb2+ includes the regulatory protein gene (PbrR) along with operator/promoter (PbrO/P) of the lead resistance operon from plasmid pMOL30. PbrO/P also controls the gfp reporter gene expression. Escherichia coli DH5α is the host organism. GFP response to induction by Pb2+ peaked at 250 μM. Decline in fluorescence beyond 250 μM was related to drop in copy number of the biosensor plasmid in the cells. A formula that estimates available Pb2+ concentration in test samples with 95% accuracy was derived by multiple regression of fluorescence and cell density values at various Pb2+ concentrations at 12 h growth. The biosensor was tested for co-inducibility by Cd2+, Zn2+ and Hg2+. Only Zn2+ showed mild induction at high concentrations and the highest fluorescence obtained was 8.5 times lower than that obtained with Pb2+. The induction method used here allows water collected from natural resources to be directly tested by using it to prepare the growth medium for the biosensor. This biosensor offers a simple and quick method for detection of available lead in the aquatic environment.
|Number of pages||6|
|Publication status||Published - Mar 25 2008|
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