A mer operon confers mercury reduction in a Staphylococcus epidermidis strain isolated from Lanzhou reach of the Yellow River

• Staphylococcus epidermidis strain Lzu-02 is able to reduce Hg (II) to Hg (0) aerobically.
• The optimum condition for Hg (II) reduction in strain Lzu-02 is pH 6 and 37 °C in M9 minimal salts medium.
• Strain Lzu-02 owns a Mer operon consisting merR, merC, merT and merA genes which are involved in Hg (II) reduction.
• Strain Lzu-02 is the first strain isolated from Lanzhou Reach of the Yellow River that is able to reduce Hg (II).

Mercury (Hg) contaminants are widespread in Lanzhou and cause environmental pollution. Mercury pollution is harmful to environments and human health. Microbes are able to reduce Hg (II) to less toxic form elemental Hg which could be a potential alternative for mercury remediation. We've isolated a strain named Lzu-02 from sediments of the Lanzhou Reach of the Yellow River which is able to resist Hg (II). It was also able to reduce Hg (II) to elemental Hg aerobically when incubated in M9 medium with 40 μM HgCl2. The optimum condition of resisting and reducing Hg (II) for Lzu-02 was pH 6 and 37 °C. Lzu-02 was identified to be most similar to Staphylococcus epidermidis by 16S sequencing analysis and Vitek phenotype identification. We also found that Lzu-02 had a mer operon consisting of SmerR, SmerC, SmerT and SmerA genes. The relative expressions of three genes (SmerC, SmerT and SmerA) were upregulated when Lzu-02 was cultivated in M9 medium with 40 μM HgCl2. These results suggested that strain Lzu-02 could be useful for the bioremediation of Hg (II) in Lanzhou reach of the Yellow River.