Abstract

 Mercury resistant Escherichia coli strains have been isolated from different mercury polluted sites of India and their minimum inhibitory concentration (MIC) levels were determined for HgCl₂. Biochemical identification of E. coli strains was also performed with HiMedia’s biochemical identification kit for various biochemical assays, like, Citrate utilization, Lysine decarboxylase, Ornithine decarboxylase, Urease, Phenylalanine deamination, Nitrate reduction, H₂S production, Glucose, Adonitol, Lactose, Arabinose, Sorbitol etc. The zone of inhibition was measured to find the antibiotic susceptibility level. The location of mer operon [containing mergenes including merA responsible for the expression of mercuric reductase enzyme (MerA) which converts the toxic Hg²⁺ to least toxic elemental Hg⁰] was determined by transforming the isolated plasmids into mercury sensitive host E. coliDH5α cells. Plasmid isolated from transformed E. coli DH5α cells were also analyzed and compared with the plasmid profile of the wild-type E. coli strains. Oligonucleotides primer were designed by comparing the known reported sequences of merA from Gram-negative bacteria (Escherichia coli plasmid R100) and 1695 bp of merA gene was amplified by PCR.

Key words: Mercury resistant, Escherichia coli, minimum inhibitory concentration (MIC), mer operon, merA.