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

Abstract

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.

Mercury Resistance and Removal Mechanisms of Pseudomonas sp. Isolated Mercury-contaminated Site in Taiwan

“…As heat shock proteins have been reported to be induced by toxic metals (Cassier-Chauva and Chauvat, 2015), five genes coding for heat shock proteins and five genes coding for chaperons identified in this study were suggested to be able to protect bacterial cells from Hg stress due that they are known to assist in protein folding and reintegration into the membrane. The mer operon is one of the most widely distributed in the Hg detoxification genetic system (Mathema et al, 2011). …”

Diversity of Mercury Resistant Escherichia coli Strains Isolated from Aquatic Systems in Rio de Janeiro, Brazil

“…The genetic system evolved as mer operon is the only well-known bacterial mercury resistance system with high yield transformation of its toxic target into volatile nontoxic forms [27,31,[33][34][35], particularly in Gram-negative bacteria [14,22]. The mer locus is found to be widely distributed among bacterial lineages, and mer-like sequences have been described.…”

“…The mer locus is found to be widely distributed among bacterial lineages, and mer-like sequences have been described. Several biochemical mechanisms are identified, and the complexity among the ecological niche of mercury-resistant microbes is still not fully described [10,35]. merA plays a key role on mercury resistance of bacterial community exposed to mercury contamination, but the combinatorial action of genetic determinants seems to confer a broad spectrum mercury detoxification system [10,35].…”

“…Several biochemical mechanisms are identified, and the complexity among the ecological niche of mercury-resistant microbes is still not fully described [10,35]. merA plays a key role on mercury resistance of bacterial community exposed to mercury contamination, but the combinatorial action of genetic determinants seems to confer a broad spectrum mercury detoxification system [10,35]. So, the involvement of additional genetic determinants not investigated here, acting as effectors or regulators genes, must be considered for the expression of mercury resistance phenotype among merA negative E. coli strains.…”

Presencia de bacterias rizosféricas resistentes a mercurio en suelos del sur de Bolívar, Colombia

“…El mecanismo de resistencia más ampliamente descripto para este metal se basa en la presencia de grupos de genes organizados en un único operón, denominado "operón mer", que permite la detoxificación enzimática del metal conocido hasta el momento que permite la transformación de formas tóxicas a formas no toxicas volátiles (MATHEMA et al, 2011).…”