Isolation and characterization of mercury resistant marine bacteria from the coastal area of Chennai, India

Among all the heavy metals, Mercury (Hg) has no known essential biological function and is extremely toxic. Despite the fact that estuarine sediments are often severely polluted with mercury, only a limited number of studies have focused on the mechanisms of adaptation in marine sediment microbial communities to mercury contamination. Metal-resistant microorganisms may be useful as indicators of potential toxicity to other forms of life and are important in studies of mechanisms, determinants and genetic transfer of microbial metal-resistance. The primary objective of this study was to isolate and enumerate mercury-resistant bacteria from various locations in the coastal regions of Chennai. Seventy marine bacteria were isolated from Sea water and sediments collected from three different locations. Bacteria highly resistant to mercury (BHRM) isolated from seawater and sediment samples were tested for their growth in the presence of different concentrations of mercury and other heavy metals. It has been found that 5 marine bacteria were highly resistant to all the heavy metals tested. These BHRM were characterized morphologically and biochemically. These strains have been subjected to plasmid curing and the same has confirmed that these strains are having mercury resistance which may be plasmid mediated. The hypothesis put forth for this study that bacterial strains capable of Hg resistance can also tolerate, detoxify or biotransform a variety of other toxicants.