Volatilization of Metal Mercury from Organomercurials by Highly Mercury-Resistant Acidithiobacillus ferrooxidans MON-1

The iron-oxidizing bacterium Acidithiobacillus ferrooxidans MON-1 is highly resistant not only to mercuric chloride (HgCl2) but also to organomercurials such as methylmercury chloride (MMC). We have found that cytochrome c oxidase, purified from strain MON-1, reduces Hg2+ to volatilizable metal mercury (Hg-0) with reduced mammalian cytochrome c or Fe2+ as an electron donor. In this study we found that cytochrome c oxidase can volatilize Hg-0 from MMC as well as from Hg2+ with reduced mammalian cytochrome c or c-type cytochrome purified from strain MON-1 as an electron donor. We also found that MMC-Hg-0 volatilization activity is present in the MON-1 plasma membrane but not in the cytosol. These activities were strongly inhibited by sodium cyanide (NaCN) and the antibody produced against purified MON-1 cytochrome C oxidase. This is the first report to indicate that cytochrome c oxidase is involved in the degradation of organomercurials in microorganisms.