Herschy Barry, Whicher Alexandra, Camprubi Eloi, Watson Cameron, Dartnell Lewis, Ward John, Evans Julian R G, Lane Nick
Department of Genetics, Evolution and Environment, University College London, London, UK.
J Mol Evol. 2014 Dec;79(5-6):213-27. doi: 10.1007/s00239-014-9658-4. Epub 2014 Nov 27.
Chemiosmotic coupling is universal: practically all cells harness electrochemical proton gradients across membranes to drive ATP synthesis, powering biochemistry. Autotrophic cells, including phototrophs and chemolithotrophs, also use proton gradients to power carbon fixation directly. The universality of chemiosmotic coupling suggests that it arose very early in evolution, but its origins are obscure. Alkaline hydrothermal systems sustain natural proton gradients across the thin inorganic barriers of interconnected micropores within deep-sea vents. In Hadean oceans, these inorganic barriers should have contained catalytic Fe(Ni)S minerals similar in structure to cofactors in modern metabolic enzymes, suggesting a possible abiotic origin of chemiosmotic coupling. The continuous supply of H2 and CO2 from vent fluids and early oceans, respectively, offers further parallels with the biochemistry of ancient autotrophic cells, notably the acetyl CoA pathway in archaea and bacteria. However, the precise mechanisms by which natural proton gradients, H2, CO2 and metal sulphides could have driven organic synthesis are uncertain, and theoretical ideas lack empirical support. We have built a simple electrochemical reactor to simulate conditions in alkaline hydrothermal vents, allowing investigation of the possibility that abiotic vent chemistry could prefigure the origins of biochemistry. We discuss the construction and testing of the reactor, describing the precipitation of thin-walled, inorganic structures containing nickel-doped mackinawite, a catalytic Fe(Ni)S mineral, under prebiotic ocean conditions. These simulated vent structures appear to generate low yields of simple organics. Synthetic microporous matrices can concentrate organics by thermophoresis over several orders of magnitude under continuous open-flow vent conditions.
实际上所有细胞都利用跨膜的电化学质子梯度来驱动ATP合成，为生物化学过程提供能量。自养细胞，包括光合生物和化能无机营养生物，也利用质子梯度直接为碳固定提供能量。化学渗透偶联的普遍性表明它在进化过程中很早就出现了，但其起源尚不清楚。碱性热液系统在深海热液喷口内相互连接的微孔的薄无机屏障上维持着自然质子梯度。在冥古宙海洋中，这些无机屏障应该含有结构与现代代谢酶中的辅因子相似的催化性Fe(Ni)S矿物，这表明化学渗透偶联可能有非生物起源。分别来自热液流体和早期海洋的H2和CO2的持续供应，与古代自养细胞的生物化学有进一步的相似之处，特别是古菌和细菌中的乙酰辅酶A途径。然而，自然质子梯度、H2、CO2和金属硫化物驱动有机合成的确切机制尚不确定，理论观点缺乏实证支持。我们构建了一个简单的电化学反应器来模拟碱性热液喷口的条件，以研究非生物喷口化学能否预示生物化学起源的可能性。我们讨论了反应器的构建和测试，描述了在模拟前生物海洋条件下含有镍掺杂的马基诺矿（一种催化性Fe(Ni)S矿物）的薄壁无机结构的沉淀过程。这些模拟喷口结构似乎能产生低产率的简单有机物。在连续开放流动的喷口条件下，合成微孔基质可以通过热泳将有机物浓缩几个数量级。
