Growth substrates that maximize energy yield are widely thought to be utilized preferentially by microorganisms. However, observed distributions of microorganisms and their activities often deviate from predictions based solely on thermodynamic considerations of substrate energy supply. Here we present observations of the bioenergetics and growth yields of a metabolically flexible, thermophilic strain of the archaeon Acidianus when grown autotrophically on minimal medium with hydrogen (H₂) or elemental sulfur (S°) as an electron donor, and S° or ferric iron (Fe³⁺) as an electron acceptor. Thermodynamic calculations indicate that S°/Fe³⁺ and H₂/Fe³⁺ yield three- and fourfold more energy per mole of electrons transferred, respectively, than the H₂/S° couple. However, biomass yields in Acidianus cultures provided with H₂/S° were eightfold greater than when provided S°/Fe³⁺ or H₂/Fe³⁺, indicating that the H₂/S° redox couple is preferred. Indeed, cells provided with all three growth substrates (H₂, Fe³⁺ and S°) grew preferentially by reduction of S° with H₂. We conclude that substrate preference is dictated by differences in the energy demand of electron transfer reactions in Acidianus when grown with different substrates, rather than substrate energy supply.

中文翻译：

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微生物底物的偏好取决于能量需求而不是供应

人们普遍认为，使能量产量最大化的生长基质优先被微生物利用。然而，观察到的微生物分布及其活动常常偏离仅基于底物能量供应的热力学考虑的预测。在这里，我们介绍古生酸菌的代谢灵活，嗜热菌株的生物能学和生长产量的观察，这些菌株在以氢（H ₂）或元素硫（S°）为电子供体，以S°或三价铁为基本培养基时自养生长铁（Fe ³⁺）作为电子受体。热力学计算表明S°/ Fe ³⁺和H ₂ / Fe ³⁺每摩尔转移的电子产生的能量分别比H ₂ / S°对高三到四倍。然而，提供H ₂ / S°的酸性培养物中生物量产率比提供S°/ Fe ³⁺或H ₂ / Fe ³⁺时高八倍，表明H ₂ / S°氧化还原对是优选的。实际上，具有所有三种生长底物（H ₂，Fe ³⁺和S°）的细胞优先通过用H ₂还原S°优先生长。我们得出的结论是，底物的偏爱是由Acidianus中电子转移反应的能量需求差异决定的 当与不同的底物一起生长时，而不是底物能量供应上。