Detection of mercuric reductase (MerA) gene from Micrococcus sp. isolated from Signy Island, Antarctica

Mercury (Hg) is a heavy metal that can be released into the environmentthrough natural activity such as volcanic eruptions and release from vegetation during bushfires, and anthropogenic activities such as the gold mining process and fossil fuel burning. Most atmospheric mercury is elemental Hg (Hg0), which is less toxic than the Hg2+ ion. However, elemental Hg can be oxidised to amore toxic form through interaction with ozone in the presence of water. Certain microbes are capable of enzymic reduction of Hg2+ to Hg0 using mercuric reductase, coded for by the merAgene.In this study, we screened the gene from bacterial strains isolated from soil collected at Signy Island, South Orkney Islands, maritime Antarctic, a gold mine in Sumbawa Island in Indonesia and a tin mine at Guar Perahu, Malaysia. A total of seven bacterial strains were isolated. One strain was isolated from the tin mine, and three each from the gold mine and Signy Island. The genewas absent from all the strains isolated from Sumbawa and Guar Perahu, but the gene was detected from an isolate from Signy Island. Based on analysis of the strain’s 16S rRNA gene, it was assigned to the genus Micrococcus (similarity 97.22%) compared with the global recorded database at the National Centre for Biotechnology Information (NCBI) using the BLAST program. We thereby confirmed the presence of the genein this bacterial strain, providing the first identification of this mercury-reducing gene in Signy Island microbiota.