Development of a novel biosensor for the detection of arsenic in drinking water

We sought to develop a whole-cell biosensor for the detection of arsenic in drinking water, a major problem in Bangladesh and West Bengal. In contrast to previously described systems, our biosensor would give a pH change as output, allowing simple detection with a pH electrode or pH indicator solution. We designed and modelled a system based on the arsenate-responsive promoter of the Escherichia coli arsenic detoxification system, using urease to increase pH in the absence of arsenate, and β-galactosidase (LacZ) to decrease pH in the presence of arsenate. The pH-reducing β-galactosidase part of the system was constructed and tested, and was found to give a clear response to arsenate concentrations as low as 5 ppb arsenic, well below the World Health Organisation (WHO) recommended limit of 10 ppb.