Bacterial mer operon-mediated detoxification of mercurial compounds: a short review.

Mercury pollution has emerged as a major problem in industrialized zones and presents a serious threat to environment and health of local communities. Effectiveness and wide distribution of mer operon by horizontal and vertical gene transfer in its various forms among large community of microbe reflect importance and compatibility of this mechanism in nature. This review specifically describes mer operon and its generic molecular mechanism with reference to the central role played by merA gene and its related gene products. The combinatorial action of merA and merB together maintains broad spectrum mercury detoxification system for substantial detoxification of mercurial compounds. Feasibility of mer operon to coexist with antibiotic resistance gene (ampr, kanr, tetr) clusters enables extensive adaptation of bacterial species to adverse environment. Flexibility of the mer genes to exist as intricate part of chromosome, plasmids, transposons, and integrons enables high distribution of these genes in wider microbial gene pool. Unique ability of this system to manipulate oligodynamic property of mercurial compounds for volatilization of mercuric ions (Hg2+) makes it possible for a wide range of microbes to tolerate mercury-mediated toxicity.