Biogeosciences Discuss., 8, 2851-2874, 2011
www.biogeosciences-discuss.net/8/2851/2011/
doi:10.5194/bgd-8-2851-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Effects of copper mineralogy and methanobactin on cell growth and sMMO activity in Methylosinus trichosporium OB3b
E. Chi Fru1, N. D. Gray1, C. McCann1, J. de C. Baptista1, B. Christgen1, H. M. Talbot1, A. El Ghazouani2, C. Dennison2, and D. W. Graham1
1School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
2Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK

Abstract. Controls on in situ methanotroph activity are not well understood. One potentially important parameter is copper (Cu) because this metal is at the centre of particulate methane monooxygenase (pMMO), the most active enzyme involved in oxidizing methane to methanol. Furthermore, Cu-to-cell ratios influence the relative expression of pMMO versus the alternate soluble MMO (sMMO) in some species. Most methanotroph studies have only assessed readily soluble forms of Cu (e.g., CuCl2) atypical of real methanotroph habitats and there is a dearth of activity data associated with more common environmental Cu sources. Here we quantified sMMO activity and growth kinetics in Methylosinus trichosporium OB3b, an organism that expresses both pMMO and sMMO, when grown on Cu-minerals with differing dissolution equilibria to assess how mineral source and methanobactin (mb) influences growth. Mb is a molecule produced by M. trichosporium OB3b that has a high affinity for Cu, reduces Cu toxicity, mediates Cu uptake and may be key to Cu availability in terrestrial systems. Abiotic Cu-dissolution experiments showed that Cu release is affected by mb level, although mb only enhances Cu dissolution from sparingly soluble minerals, such as CuO and to a greater extent CuCO3·Cu(OH)2. However, the two minerals affected M. trichosporium OB3b growth very differently. Cells grew without growth lag and with active pMMO on CuCO3·Cu(OH)2, regardless of the amount of mineral supplied (< 500 μmoles Cu-total L−1). In contrast, they also grew well with CuO (< 50 μmoles Cu-total L−1), but instead had active sMMO, although sMMO activity was conditionally suppressed by supplemental mb and-or direct cell-mineral contact. Mb additions significantly increased growth rates (p<0.05) with both minerals. Results show mb broadly stimulates growth, but Cu mineralogy and mb dictate whether sMMO or pMMO is active in the cells. This has implications to in situ bioremediation and other studies on methanotroph function in terrestrial systems.

Citation: Chi Fru, E., Gray, N. D., McCann, C., Baptista, J. de C., Christgen, B., Talbot, H. M., El Ghazouani, A., Dennison, C., and Graham, D. W.: Effects of copper mineralogy and methanobactin on cell growth and sMMO activity in Methylosinus trichosporium OB3b, Biogeosciences Discuss., 8, 2851-2874, doi:10.5194/bgd-8-2851-2011, 2011.
 
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