Plasmid-Borne Mercury Resistance in Aquatic Escherichia coli

Bacteria (E. coli) isolated from different aquatic bodies of India were analyzed for their tolerance to mercury (HgCl₂). Out of the 30 isolates of E. coli, collected from water samples of four geographically distinct regions and hospital settings in India, 8 strains showed significantly high levels of tolerance to the inorganic form of mercury i.e mercury chloride (HgCl₂). All the eight strains revealed the presence of a plasmid of approximately 24kb, and transformation of the isolated plasmids into the mercury-sensitive competent cells of E. coli DH5α rendered the transformants resistant to the same concentration of mercury as wild type-strains.