Gut bacteria genetically modified to glow when they sense arsenic could be used to detect contaminated water, which is a major public health threat in Bangladesh, India, Vietnam and China.
Existing chemical tests for arsenic are unreliable, especially at low but still dangerous concentrations. A better approach is to exploit bacteria's natural sensitivity to arsenic, says Jan Roelof van der Meer of the Swiss Federal Institute for Environmental Science and Technology, who led the research.
The modified bacteria are now undergoing trials in Vietnam. And at just two US cents to produce, they could offer a cheap way to detect arsenic contamination in developing countries.