Báo cáo khoa học: Bioenergetics of the formyl-methanofuran dehydrogenase and heterodisulfide reductase reactions in Methanothermobacter thermautotrophicus

Bioenergetics of the formyl-methanofuran dehydrogenase and heterodisulfide reductase reactions in Methanothermobacter thermautotrophicus

Authors: Linda M. I. de Poorter, Wim G. Geerts, Alexander P. R. Theuvenet, and Jan T. Keltjens

Field: Microbiology, Cell Biology

Document Content:

This study investigates the bioenergetics of two critical H2-dependent reactions in the energy metabolism of methanogenic archaea, specifically in Methanothermobacter thermautotrophicus. These reactions are the synthesis of formyl-methanofuran and the reduction of heterodisulfide (CoM-S-S-CoB). The research was conducted using chemostat cultures and cell suspensions under varying dissolved hydrogen partial pressures (pH₂). Formyl-methanofuran synthesis was found to be an endergonic reaction (AG°’ = +16 kJ·mol⁻¹), with experimental free energy changes (AG’) ranging from +10 to +35 kJ·mol⁻¹, influenced by pH. This suggests the reaction is driven by the import of sodium ions, with a stoichiometry of two to four. Heterodisulfide reduction (AG°’ = −40 kJ·mol⁻¹) exhibited more negative free energy changes, ranging from -55 to -80 kJ·mol⁻¹. These changes were in equilibrium with the proton motive force, indicating the translocation of three to four protons out of the cells. A notable shift in proton translocation stoichiometry occurred around a pH₂ of 0.12 bar, suggesting that methanogens regulate their bioenergetic machinery in response to environmental hydrogen concentrations.

Detailed Table of Contents:

• Introduction
• Materials and Methods
• Results
• Discussion
• Acknowledgements
• References