Potential Whole-Cell Biosensors for Detection of Metal Using MerR Family Proteins from sp. YSU and OR02.

Cell-based biosensors harness a cell's ability to respond to the environment by repurposing its sensing mechanisms. MerR family proteins are activator/repressor switches that regulate the expression of bacterial metal resistance genes and have been used in metal biosensors. Upon metal binding, a conformational change switches gene expression from off to on. The genomes of the multimetal resistant bacterial strains, Oak Ridge strain 02 ( 02) and sp. YSU, were recently sequenced. Sequence analysis and gene cloning identified three mercury resistance operons and three MerR switches in these strains. Transposon mutagenesis and sequence analysis identified sp. YSU zinc and copper resistance operons, which appear to be regulated by the protein switches, ZntR and CueR, respectively. Sequence analysis and reverse transcriptase polymerase chain reaction (RT-PCR) showed that a CueR switch appears to activate a 02 copper transport gene in the presence of CuSO and HAuCl·3HO. In previous studies, genetic engineering replaced metal resistance genes with the reporter genes for β-galactosidase, luciferase or the green fluorescence protein (GFP). These produce a color change of a reagent, produce light, or fluoresce in the presence of ultraviolet (UV) light, respectively. Coupling these discovered operons with reporter genes has the potential to create whole-cell biosensors for HgCl, ZnCl, CuSO and HAuCl·3HO.