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From 2012hs.igem.org

We plan to build an arsenic biosensor that is based upon an genetically-modified bacterium. Our biosensor will use the arsenic-sensitive promoter K190015 (Gronigen 2009) coupled with one of three chemiluminescence reporters: K3325100, K325210, and K325905 (Cambridge 2010). We plan to design and inexpensive hand held electronic luminometer to determine the level of arsenic.

The K190015 arsenic sensitive promoter is an inducible promoter that works like the lactose promoter. An inhibitor called "ArsR" is bound to a control part of the DNA and is released when arsenic binds thus allowing transcription. One problem is that the K190015 promoter seems to be always turned on. The experience of the Gronigen team is that there was fluorescence even without an input of arsenic. We found this to be true also. Newly transformed colonies of E. coli with K190015 (in the J61002-R0040 expression plasmid) immediately make RFP and purple colonies. This sensor is also not very sensitive to arsenic concentration and resquires ultraviolet light to detect the RFP.

Our plan is to use one of the chemiluminescence reporters so that our device will yield light upon detection of arsenic when in the presence of luciferin. These should be more sensitive than the fluorescence reporter and not require the input of ultraviolet light for detection. The construction of a hand held battery powered luminometer will allow us to calibrate the signal of the arsenic biosensor by the addition of known arsenic before the test for added arsenic in suspected water.