Division of Archaea Biology and Ecogenomics, Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14 UZA I, 1090 Vienna, Austria.
Institute of Molecular Evolution, Heinrich-Heine-University, Universitätsstr. 1, 40225 Düsseldorf, Germany.
Curr Opin Microbiol. 2018 Jun;43:77-83. doi: 10.1016/j.mib.2017.12.010. Epub 2018 Jan 12.
Molecular hydrogen is an ancient source of energy and electrons. Anaerobic autotrophs that harness the H/CO redox couple harbour ancient biochemical traits that trace back to the universal common ancestor. Aspects of their physiology, including the abundance of transition metals, radical reaction mechanisms, and their main exergonic bioenergetic reactions, forge links between ancient microbes and geochemical reactions at hydrothermal vents. The midpoint potential of H however requires anaerobes that reduce CO with H to use flavin based electron bifurcation-a mechanism to conserve energy as low potential reduced ferredoxins via soluble proteins-for CO fixation. This presents a paradox. At the onset of biochemical evolution, before there were proteins, how was CO reduced using H? FeS minerals alone are probably not the solution, because biological CO reduction is a two electron reaction. Physiology can provide clues. Some acetogens and some methanogens can grow using native iron (Fe) instead of H as the electron donor. In the laboratory, Fe efficiently reduces CO to acetate and methanol. Hydrothermal vents harbour awaruite, NiFe, a natural compound of native metals. Native metals might have been the precursors of electron bifurcation in biochemical evolution.
氢气是一种古老的能源和电子来源。利用 H/CO 氧化还原对的厌氧自养生物拥有古老的生化特征，可以追溯到普遍共同的祖先。它们的生理学方面，包括过渡金属的丰度、自由基反应机制以及主要的放能生物能量反应，将古老的微生物和热液喷口的地球化学反应联系起来。然而，H 的中点电位要求用 H 还原 CO 的厌氧菌利用黄素基电子分岔——一种通过可溶性蛋白质将低势能还原铁氧还蛋白作为能量保存的机制——来固定 CO。这就出现了一个悖论。在生化进化的开始，在有蛋白质之前，如何使用 H 还原 CO？仅 FeS 矿物可能不是解决方案，因为生物 CO 还原是一个两电子反应。生理学可以提供线索。一些乙酸菌和一些产甲烷菌可以利用天然铁（Fe）而不是 H 作为电子供体生长。在实验室中，Fe 可以有效地将 CO 还原为乙酸盐和甲醇。热液喷口含有天然金属的 awaruite 和 NiFe。天然金属可能是生化进化中电子分岔的前体。
