Novel approaches to biosensors for detection of arsenic in drinking water

Arsenic is a serious problem in groundwater in Bangladesh, West Bengal, and other regions, with up to 100 million people worldwide estimated to be at risk. Long term consumption leads to arsenicosis, skin lesions and cancers. There is a clear need for cheap, simple, non-toxic field test kits for routine monitoring of arsenic levels in drinking water. Whole-cell biosensors may provide a solution, but current systems require expensive reagents or laboratory equipment. Here we present two new approaches: firstly, a biosensor in which detection of arsenic is signalled as an easily detectable drop in pH; secondly, a chromogenic system using endospores, which can be stored and distributed in dried form without requiring freeze-drying or refrigeration. Further development of these concepts may lead to a cheap practical device which can be used in the field by workers with minimal training.

We have demonstrated two novel approaches to the development of whole-cell biosensors for the detection of arsenic in drinking water. Our pHbased E. coli system has very high sensitivity, and, though it requires freeze-drying, may be suitable for further development towards our ultimate goal of a cheap, simple, disposable arsenic quantification system. We also unexpectedly found that bicarbonate, a buffer ion present in groundwater, appears to increase the sensitivity of the biological arsenic-responsive promoter, for reasons which are currently unclear. We have also shown that Bacillus endospores can form the basis of an arsenic-detection system, though the current version may lack the required sensitivity for this application. We hope with further development to produce an ideal biosensor system meeting all of our goals. We are hoping soon to undertake field tests of our biosensors in conjunction with Engineers Without Borders. We will be happy to supply our Acknowledgments The authors would like to thank Dr. Garry Blakely for advice on Bacillus, Dr. Jim Philp for advice on the arsenic crisis, and to Dr. Randy Rettberg, organizer of iGEM, as well as the Gatsby Foundation, the Commission for the Royal Exhibition of 1851, the Biotechnology and Biological Sciences Research Council and the Engineering and Physical Sciences Research Council for funding.