Effects of Methanobactin on the Degradation of Methylmercury

Exposure to even small amounts of methylmercury can cause serious health problems, and is especially damaging to unborn infants as their brains and nervous systems are developing. In natural environments certain anaerobic microorganisms are the predominant cause for the production of methylmercury (MeHg) toxin. Methanobactin (MB) is a chalkophore (copper binding) secreted by some methanotrophs. The ligand set responsible for copper-binding can also bind different mercury species. The best-characterized MBs to date are those from Methylosinus trichosporium OB3b and Methylocystis strain SB2. Previous studies have indicated methanotrophs that produce and take up MB are able to degrade MeHg. We wanted to see if the presence of MB on methanotrophs that don’t produce MB such as, Mm. album BG8 wild type and ΔmbnT, Methylocystis sp. strain Rockwell, and Methylococcus capsulatus Bath, would affect MeHg degeneration. In order for MB to uptake methylmercury, a TonB-dependent transporter. Mm. album BG8 and Methylocystis sp. strain Rockwell were found to have genes similar to mbnT that encode the transporter. Experiments were performed in the absence/presence of MB from either Ms. trichosporium OB3b or Methylocystis sp. strain SB2. Our data provided evidence that some methanotrophs “steal” MB and such “theft” enhances the strains’ ability to degrade methylmercury. Both Mm. album BG8 and Methylocystis sp. strain Rockwell had increased MeHg degradation when treated with OB3b or SB2 MB than in the absence of MB. However, this was not the case for all the methanotrophs. MeHg degradation observed in Mc. capsulatus Bath, and ΔmbnT mutant of Mm. album BG8 were not significantly different in the presence or absence of either form of MB. There are many diseases associated with excess metal in the body. I’m sure the first ones that come to mind are lead and mercury poisoning, but there’s many more. There’s currently research being done for Wilson’s disease which is a rare genetic disorder characterized by excessive copper in various body tissues. Through better understanding of methanotrophic communities, we can bring the world one step closer to finding treatment for just methylmercury poisoning and other medical issues in situ.