Cloning and expression of the mercury resistance genes of marine Pseudomonas sp. strain MR1 plasmid pMR1 in Escherichia coli.

The mercury resistance determinant of marine Pseudomonas sp. strain MR1 plasmid pMR1 was cloned into a narrow-host-range vector pUC18. A direct selection of mercury resistant clones was successful and 12 clones were evolved; 9 from direct selection on mercury agar plates and 3 from ampicillin-resistant white colonies. All the predicted clones efficiently volatilized mercury. One of the hybrid plasmids pMRD5, containing a 15.5-kb insert, conferred inducible resistance to both HgCl2 and phenyl mercury acetate with over a 40-fold increase in mer resistance in Escherichia coli HB101. No DNA homology existed between the mer operon of Pseudomonas sp. strain MR1 and the characterized determinants of Tn501 mer DNA.