On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells
On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells
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DOI：
10.1098/rstb.2002.1183
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发表时间：
2003-01-29
影响因子：
6.3
通讯作者：
Russell, MJ
中科院分区：
文献类型：
--
作者：
Martin, W;Russell, MJ
所有的生命都是由细胞组成的。与环境的物理分隔和自组织的氧化还原反应是生物最保守的属性，因此具有这些属性的无机物最有可能是生命的祖先。我们建议，生活进化的结构铁单硫化物沉淀物中的渗流网站热液丘在氧化还原，pH值和温度梯度之间的硫化物丰富的热液流体和含铁（II）的沃茨的冥古宙洋底。自然产生的，三维compartmentation内观察到的结晶渗漏网站金属硫化物沉淀物表明，这些无机隔室的前体细胞壁和膜中发现的自由生活的原核生物。已知FeS和NiS能够催化热液成分一氧化碳和甲基硫化物合成乙酰基甲基硫化物，这表明在这些金属硫化物壁隔室的内表面发生了前生物合成，这进一步抑制了反应产物扩散到海洋中，提供了足够的反应物浓度，以促成从地球化学到生物化学的过渡。所谓的RNA世界的化学可能发生在这些自然形成的催化壁隔室中，以产生复制系统。足够浓度的前体，以支持复制将已合成原位地球化学和地球化学，与FeS（和NiS）中心发挥中央催化作用。我们推断的普遍祖先不是一个自由生活的细胞，而是局限于天然的化学渗透，FeS隔间内发生的合成其成分。第一个自由生活的细胞被认为是真细菌和古细菌的化能自养生物，它们在3.8 Gyr前从无机界出现。我们提出，这些原核谱系的出现从无机界限独立发生，促进膜脂质生物合成的独立起源：类异戊二烯醚膜在古细菌和脂肪酸酯膜真细菌谱系。真核生物，所有这些都是祖先异养生物，并具有真细菌脂质，被认为是出现在约。2 Gyr ago通过涉及自养古细菌宿主和异养真细菌共生体的共生，线粒体和氢化酶体的共同祖先。所有原核生物共有的属性被认为是从它们的有限的普遍祖先遗传而来的。区分真细菌和古细菌的属性，但在组内是统一的，被视为他们的分化阶段的遗迹后，从非自由生活的普遍祖先和自由生活的化能自养生活方式的起源。真核生物分别与真细菌和古细菌共有的属性被认为是通过共生遗传的。真核生物所特有的属性被视为其谱系特有的发明。真核生物内膜系统和核膜的起源被认为是真细菌膜脂合成基因表达的偶然结果，该基因由古细菌遗传装置在一个没有完全准备好容纳此类化合物的隔室中表达，导致真细菌脂质囊泡积聚在其合成位点周围的胞质溶胶中。生物界最古老的分界线是真细菌和古细菌之间的分界线，而最陡峭的进化等级则是原核生物和真核生物之间的分界线。
All life is organized as cells. Physical compartmentation from the environment and self-organization of self-contained redox reactions are the most conserved attributes of living things, hence inorganic matter with such attributes would be life's most likely forebear. We propose that life evolved in structured iron monosulphide precipitates in a seepage site hydrothermal mound at a redox, pH and temperature gradient between sulphide-rich hydrothermal fluid and iron(II)-containing waters of the Hadean ocean floor. The naturally arising, three-dimensional compartmentation observed within fossilized seepage-site metal sulphide precipitates indicates that these inorganic compartments were the precursors of cell walls and membranes found in free-living prokaryotes. The known capability of FeS and NiS to catalyse the synthesis of the acetyl-methylsulphide from carbon monoxide and methylsulphide, constituents of hydrothermal fluid, indicates that pre-biotic syntheses occurred at the inner surfaces of these metal-sulphide-walled compartments, which furthermore restrained reacted products from diffusion into the ocean, providing sufficient concentrations of reactants to forge the transition from geochemistry to biochemistry. The chemistry of what is known as the RNA-world could have taken place within these naturally forming, catalytic-walled compartments to give rise to replicating systems. Sufficient concentrations of precursors to support replication would have been synthesized in situ geochemically and biogeochemically, with FeS (and NiS) centres playing the central catalytic role. The universal ancestor we infer was not a free-living cell, but rather was confined to the naturally chemiosmotic, FeS compartments within which the synthesis of its constituents occurred. The first free-living cells are suggested to have been eubacterial and archaebacterial chemoautotrophs that emerged more than 3.8 Gyr ago from their inorganic confines. We propose that the emergence of these prokaryotic lineages from inorganic confines occurred independently, facilitated by the independent origins of membrane-lipid biosynthesis: isoprenoid ether membranes in the archaebacterial and fatty acid ester membranes in the eubacterial lineage. The eukaryotes, all of which are ancestrally heterotrophs and possess eubacterial lipids, are suggested to have arisen ca. 2 Gyr ago through symbiosis involving an autotrophic archaebacterial host and a heterotrophic eubacterial symbiont, the common ancestor of mitochondria and hydrogenosomes. The attributes shared by all prokaryotes are viewed as inheritances from their confined universal ancestor. The attributes that distinguish eubacteria and archaebacteria, yet are uniform within the groups, are viewed as relics of their phase of differentiation after divergence from the non-free-living universal ancestor and before the origin of the free-living chemoautotrophic lifestyle. The attributes shared by eukaryotes with eubacteria and archaebacteria, respectively, are viewed as inheritances via symbiosis. The attributes unique to eukaryotes are viewed as inventions specific to their lineage. The origin of the eukaryotic endomembrane system and nuclear membrane are suggested to be the fortuitous result of the expression of genes for eubacterial membrane lipid synthesis by an archaebacterial genetic apparatus in a compartment that was not fully prepared to accommodate such compounds, resulting in vesicles of eubacterial lipids that accumulated in the cytosol around their site of synthesis.Under these premises, the most ancient divide in the living world is that between eubacteria and archaebacteria, yet the steepest evolutionary grade is that between prokaryotes and eukaryotes.