Direct inhibition of methanogenesis by ferric iron

Authors

  • Peter M. van Bodegom,

    Corresponding author
    1. Laboratory of Microbiology, Wageningen University, H.v. Suchtelenweg 4, 6703 CT Wageningen, The Netherlands
    2. Laboratory of Theoretical Production Ecology, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands
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  • Johannes C.M. Scholten,

    1. Department of Biological Sciences, Pacific Northwest National Laboratory, P.O. Box 999, MS P7-50, Richland, WA 99532, USA
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  • Alfons J.M. Stams

    1. Laboratory of Microbiology, Wageningen University, H.v. Suchtelenweg 4, 6703 CT Wageningen, The Netherlands
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*Corresponding author. Present address: Department of Systems Ecology, Institute of Ecological Science, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. Tel.: +31-20-4446964; fax: +31-20-4447123, E-mail address: peter.van.bodegom@ecology.falw.vu.nl

Abstract

Observed inhibition of methanogenesis under Fe(III)-reducing conditions is usually explained by competition of methanogens and Fe(III)-reducing bacteria for the common substrates acetate and hydrogen. However, substrate competition alone cannot explain the strong inhibition of methanogenesis during Fe(III)-reduction. We demonstrate direct inhibition of methanogenesis by amorphous Fe(OH)3 at concentrations between 0 and 10 mM in experiments with pure cultures of methanogens. The sensitivity toward Fe(III) was higher for Methanospirillum hungatei and Methanosarcina barkeri grown with H2/CO2 than for Methanosaeta concilii and Methanosarcina barkeri grown with acetate. Cultures of Methanosarcina barkeri grown with H2/CO2 and methanol demonstrated a capacity for Fe(III) reduction, which suggests that Fe(III)-reduction by methanogens may also contribute to Fe(III) inhibition of methanogenesis. Our results have important implications for kinetic modelling of microbial redox processes in anoxic soils and sediments.

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