Bacterial Resistance to Mercury: A Mini-Review

With the increase in mercury pollution around the world, several bacteria have been identified that are capable of resisting mercury toxicity. With this in mind, the aim of this review was to determine which genes are involved in mercury resistance, which bacterial genera exhibit this resistance and which bacterial isolation sources have been most reported. To answer these questions, the PICO method (population, intervention, comparison and outcome) was used, three databases were searched and 17 relevant articles were included. As a result, resistance is due to a set of mer genes that transcribe mer proteins. The most important genes identified were merA and merR, and their proteins confer resistance by reducing Hg to Hg+2 or Hg0. Among the bacteria studied, those of the genera Pseudomonas, Escherichia and the phylum Cyanobacteria stand out, the most important being Escherichia coli and Synechocystis sp. which are highly efficient and fast at reducing Hg. Based on the results, Escherichia coli and Synechocystis sp. are promising candidates for reducing environmental Hg, especially in aquatic environments. However, there is a lack of studies on the mechanism of bioremediation carried out by cyanobacteria and the influence of abiotic factors on the presence and/or expression of mer genes.