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In parallel to continuous development of increasingly more sophisticated physical and chemical analytical technologies for the detection of environmental pollutants, there's a progressively more urgent need also for bioassay which report not only on the presence of a chemical but also on its bioavailability and its biological effects. As a partial fulfillment of that need, there's been a rapid development of biosensors based on genetically engineered bacteria. Natural water was polluted by arsenic that known toxin and carcinogen leaded us to designing a whole cell bacterial biosensor to detect arsenic in liquid solutions. Methods: In order to construct the biosensor, chromosomal arsR gene and its related promoter/operator from Escherichia coli strain Bl21(DE3), gfp gene as the reporter, plasmid pUC19 as the basic vector and different molecular and genetic engineering techniques such as PCR, gene cloning, etc. were applied to make the Escherichia coli strain BL21(DE3) act as the arsenic whole cell biosensor. Arsenic detection by using this biosensor was done by means of microscopy and fluorometery techniques. Strain BL21(DE3) responded mainly to As(III) and As(V) with the lowest detectable concentration being 5 μM during a 3- hours exposure and 1 and 3 μM respectively, with an 6-hours induction period. Results: Our result demonstrate that the nonpathogenic bacterial biosensors developed in the present study could be useful and applicable in determining the bioavailability of arsenic with high sensitivity in contaminated water samples after further optimization, and they suggest a potential for its inexpensive application in field-ready tests. Conclusion: Our success in designing and producing this biosensor, in addition to localizing this useful technology, will be a very large and effective step to improve the health status of drinking water, through to speed up detection of arsenic contamination of water resources. It can also attract lots of academic and industrial heads for research in this interesting field of science and establish an optimistic future in developing biosensor technology in our country.

     

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