Biomolecular Engineering of Escherichia coli Organo-mercurial Lyase Gene and its Expression

Abstract

Studies were carried out to characterize merB gene from five wild type strains of broad-spectrum Escherichia coli, collected from five geographically distinct regions of India. Each strain produced 23kb plasmid from which functional merB gene (O.64kb) was peR amplified. The merB gene from isolate GI8, which tolerated highest concentration of organic form (PMA) of mercury was cloned in high expression vector pQE30 and pGEMT-Easy vector. The transformants obtained demonstrated varied results in their appropriate hosts. The transformants (IAxpress) carrying merB gene cloned in pQE30 and negative control having pQE30 without merB insert did not grow on agar plates amended with I)lg/ml PMA. Due to the hyperexpression of merB in pQE30 most of the protein was found in nonfunctional inclusion bodies and did not show any resistance as sensitive strain (Devoid of merB gene) against PMA. On the other hand transformants of merB cloned pGEMT vector tolerated up to 5)lg/ml of PMA, which indicates that low expression of merB in this vector produces a functional product and thus tolerates five times more PMA than sensitive strain. The results demonstrate that this gene can be better exploited for bioremediation of toxic form of mercury in polluted water bodies.