Cloning of Mercuric Reductase (merA) Gene Isolated from Wild Strains of Escherichia coli

Bacterial plasmids encode resistance systems for toxic metal ions including Hg²⁺ functioning by energy – dependent efflux of toxic ions. The inducible mercury resistance (mer) operon encodes both a mercuric ion uptake and detoxification enzymes. In Gram-negative bacteria especially in E. coli, a periplasmic protein, MerP, an inner-membrane transport protein, MerT, and a cytoplasmic enzyme, mercuric reductase (the merA protein), are responsible for the transport of mercuric ions into cell and their reduction to elemental mercury, Hg°. Phytoremediation involves the use of plants to extract, detoxify and/or sequester environmental pollutants from soil and water. Transgenic plants cleave mercury ions from methyl-mercury complexes; reduce mercury ions to the metallic form; take up metallic mercury through their ischolar_mains; and evolve less toxic elemental mercury. PCR were performed to detect 1695 bp of mercuric reductase gene (merA), which is mainly responsible for the conversion of mercuric (Hg⁺²) and mercurous (Hg⁺¹) ions into non-toxic elemental mercury. PCR products of putative merA genes form environmental E.coli strains were purified and cloned into a suitable plant expression vector like pB1121 or pCAMBIA. The construct will be transformed in calli of Nicotiana plants. Expression of merA gene in transgenic plants might provide an ecologically compatible approach for the remediation of mercury pollution.