Development and testing of a green fluorescent protein-based bacterial biosensor for measuring bioavailable arsenic in contaminated groundwater samples.

A green fluorescent protein (GFP)-based bacterial biosensor for the detection of bioavailable As(III), As(V), and Sb(III) was developed and characterized. The biosensor strain Escherichia coli DH5alpha (pVLAS1) was developed based on the expression of gfp under the control of the ars promoter and the arsR gene of Staphylococcus aureus plasmid pI258. Strain DH5alpha (pVLAS1) responded mainly to As(III), As(V), and Sb(III), with the lowest detectable concentrations being 0.4, 1, and 0.75 microM, respectively, during a 2-h exposure and 0.1 microM for all three metal ions with an 8-h induction period. To assess its applicability for analyzing environmentally relevant samples, the biosensor was field-tested on shallow-well groundwater for which contaminant levels were known. Our results demonstrate that the nonpathogenic bacterial biosensor developed in the present study is useful and applicable in determining the bioavailability of arsenic with high sensitivity in contaminated groundwater samples, and they suggest a potential for its inexpensive application in field-ready tests.