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

Abstract

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 (Hg⁰) with reduced mammalian cytochrome c or Fe²⁺ as an electron donor. In this study we found that cytochrome c oxidase can volatilize Hg⁰ 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-Hg⁰ 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.