Research ArticleENVIRONMENTAL STUDIES

Methylmercury uptake and degradation by methanotrophs

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Science Advances  31 May 2017:
Vol. 3, no. 5, e1700041
DOI: 10.1126/sciadv.1700041
  • Fig. 1 Methylmercury (CH3Hg+) sorption, degradation, and species distribution.

    (A) CH3Hg+ sorption kinetics and (B) Hg species distributions (at 4 and 120 hours) by methanotrophs M. trichosporium OB3b and M. capsulatus (MC) Bath in 5 mM MOPS buffer. The total added CH3Hg+ concentration (HgT) was 5 nM at t = 0, and the cell concentration was 108 cells ml−1. CH3Hg+sol, soluble CH3Hg+; CH3Hg+ad, cell surface–adsorbed CH3Hg+; CH3Hg+up, cell uptake of or internalized CH3Hg+. IHg results from degradation of CH3Hg+. Error bars represent 1 SD from triplicate samples.

  • Fig. 2 Time- and concentration-dependent degradation of methylmercury (CH3Hg+) by methanotrophs.

    (A and B) M. trichosporium OB3b at 30°C and (C and D) M. capsulatus Bath at 45°C in 5 mM MOPS buffer. The added cell concentration was 108 cells ml−1 (washed), and the CH3Hg+ concentration was varied from 0 to 125 nM. Data points at 5 nM CH3Hg+ in (A) represent an average of replicate samples (10 to 15) from five independent batch experiments, and all other data points represent an average of triplicate samples. Error bars represent 1 SD from all replicate samples.

  • Fig. 3 Methylmercury (CH3Hg+) degradation by different methanotrophs and mutants.

    Comparisons of the time-dependent degradation of CH3Hg+ by washed cells of M. trichosporium OB3b and its mutant strains (mbnA::Gmr and ΔmbnAN), M. capsulatus Bath, and M. parvus OBBP in 5 mM MOPS buffer. The added cell concentration was 108 cells ml−1, and the CH3Hg+concentration was ~5 nM. Data points represent an average of all replicate samples (3 to 15), and error bars represent 1 SD.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/5/e1700041/DC1

    table S1. Methylmercury degradation by washed cells of methanotrophs, including M. trichosporium OB3b and its two methanobactin (mb) defective mutants (mbnA::Gmr and ΔmbnAN), Methylocystis strain SB2, M. capsulatus Bath, and M. parvus OBBP in 5 mM MOPS at pH 7.3.

    fig. S1. Methylmercury (CH3Hg+) and inorganic mercury (IHg) species distribution during CH3Hg+ degradation assays with M. trichosporium OB3b.

    fig. S2. Effects of acetylene addition (as an inhibitor of MMOs) on methylmercury (CH3Hg+) degradation by washed cells of M. trichosporium OB3b (108 cells ml−1) in 5 mM MOPS buffer at 30°C.

    fig. S3. Reactions between methylmercury (CH3Hg+, 5 nM) and purified methanobactin (1 μM) from M. trichosporium OB3b in 5 mM MOPS buffer (pH 7.3) at 30°C.

    fig. S4. Effects of methanol addition on methylmercury (CH3Hg+) degradation by washed cells of M. trichosporium OB3b (108 cells ml−1) in 5 mM MOPS buffer at 30°C.

  • Supplementary Materials

    This PDF file includes:

    • table S1. Methylmercury degradation by washed cells of methanotrophs, including M. trichosporium OB3b and its two methanobactin (mb) defective mutants (mbnA::Gmr and ΔmbnAN), Methylocystis strain SB2, M. capsulatus Bath, and M. parvus OBBP in 5 mM MOPS at pH 7.3.
    • fig. S1. Methylmercury (CH3Hg+) and inorganic mercury (IHg) species distribution during CH3Hg+ degradation assays with M. trichosporium OB3b.
    • fig. S2. Effects of acetylene addition (as an inhibitor of MMOs) on methylmercury (CH3Hg+) degradation by washed cells of M. trichosporium OB3b (108 cells ml−1) in 5 mM MOPS buffer at 30°C.
    • fig. S3. Reactions between methylmercury (CH3Hg+, 5 nM) and purified methanobactin (1 μM) from M. trichosporium OB3b in 5 mM MOPS buffer (pH 7.3) at 30°C.
    • fig. S4. Effects of methanol addition on methylmercury (CH3Hg+) degradation by washed cells of M. trichosporium OB3b (108 cells ml−1) in 5 mM MOPS buffer at 30°C.

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