Biology and Fertility of Soils

, Volume 19, Issue 1, pp 65–72

Competition for electron donors among nitrate reducers, ferric iron reducers, sulfate reducers, and methanogens in anoxic paddy soil

Authors

  • Christof Achtnich
    • Max-Planck Institut für Terrestrische Mikrobiologie
  • Friedhelm Bak
    • Max-Planck Institut für Terrestrische Mikrobiologie
  • Ralf Conrad
    • Max-Planck Institut für Terrestrische Mikrobiologie
Original Paper

DOI: 10.1007/BF00336349

Cite this article as:
Achtnich, C., Bak, F. & Conrad, R. Biol Fertil Soils (1995) 19: 65. doi:10.1007/BF00336349

Abstract

Slurries of anoxic paddy soil were either freshly prepared or were partially depleted in endogenous electron donors by prolonged incubation under anaerobic conditions. Endogenous NO3was reduced within 4 h, followed by reduction of Fe3+ and SO42−, and later by production of CH4. Addition of NO3slightly inhibited the production of Fe2+ in the depleted but not in the fresh paddy soil. Inhibition was overcome by the addition of H2, acetate, or a mixture of fatty acids (and other compounds), indicating that these compounds served as electron donors for the bacteria reducing NO3and/or ferric iron. Addition on NO3also inhibited the reduction of SO42−in the depleted paddy soil. This inhibition was only overcome by H2, but not by acetate or a mixture of compounds, indicating that H2 was the predominant electron donor for the bacteria involved in NO3and/or SO42−reduction. SO42−reduction was also inhibited by exogenous Fe3+, but only in the depleted paddy soil. This inhibition was overcome by either H2, acetate, or a mixture of compounds, suggesting that they served as electron donors for reduction of Fe3+ and/or SO42+. CH4 production was inhibited by NO3both in depleted and in fresh paddy soil. Fe3+ and SO42−also inhibited methanogenesis, but the inhibition was stronger in the depleted than in the fresh paddy soil. Inhibition of CH4 production was paralleled by a decrease in the steady state concentration of H2 to a level which provided a free enthalpy of less than ΔG=−17 kJ mol-1 CH4 compared to more than ΔG=−32 kJ mol-1 CH4 in the control. The results indicate that in the presence of exogenous fe3+ or SO42+, methanogenic bacteria were outcompeted for H2 by bacteria reducing Fe3+ or SO42+.

Key words

Nitrate reductionSulfate reductionFerric iron reductionMethanogenesisHydrogenGibbs free energy

Copyright information

© Springer-Verlag 1995