File:Plasmid Map.png

This plasmid map displays all the elements for the recombinant plasmid to be transformed into E. coli. All elements are contained in the plasmid Coli Comet Cassette-stuffer_Amp-HC (available from DNA 2.0) except for the arsR elements (colored yellow). The arsR promoter precedes arsR and GFP. arsR produces a repressor protein that binds to the arsR promoter. When arsR levels are sufficiently high, transcription is repressed until arsenic binds to these repressors and allows transcription to start. Therefore, GFP transcription will only occur in the presence of arsenic. This mechanism is originally from the ars operon in E. Coli. This operon consists of five genes: arsR, arsD, arsA, arsB, and arsC (Suzuki et al. 1998. Expression and Regulation of the Arsenic Resistance Operon of Acidiphilium multivorum AIU 301 Plasmid pKW301 in Escherichia coli. Appl Environ Microbiol. 64(2): 411–418). The first two encode repressor proteins that repress transcription of the entire set of genes. The last three encode proteins that transport arsenic out of the cell (Carlin, A., Shi, W., Rosen, B.P. 1995. The ars Operon of Escherichia coli Confers Arsenical and Antimonial Resistance. Journal of Bacteriology. 177(4): 981-986). These resistance proteins are only expressed in the presence of arsenic. To make our reporter plasmid, we replaced the resistance genes with GFP.