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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >The last eukaryotic common ancestor (LECA): Acquisition of cytoskeletal motility from aerotolerant spirochetes in the Proterozoic Eon
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The last eukaryotic common ancestor (LECA): Acquisition of cytoskeletal motility from aerotolerant spirochetes in the Proterozoic Eon

机译：最后一个真核祖先（LECA）：从元古代的耐气螺旋体中获取细胞骨架运动

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We develop a symbiogenetic concept of the origin of eukaryotic intracellular motility systems from anaerobic but aerotolerant spirochetes in sulfide-rich environments. The last eukaryotic common ancestors (LECAs) have extant archaeprotist descendants: motile nucleated cells with Embden-Meyerhof glycolysis and substrate-level phosphorylation that lack the α-proteobacterial symbiont that became the mitochondrion. Swimming and regulated O2-tolerance via sulfide oxidation already had been acquired by sulfidogenic wall-less archaebacteria (thermoplasmas) after aerotolerant cytoplasmic-tubule-containing spirochetes (eubacteria) attached to them. Increasing stability of sulfide-oxidizing/sulfur-reducing consortia analogous to extant sulfur syntrophies (Thiodendron) led to fusion. The eubacteria–archaebacteria symbiosis became permanent as the nucleus evolved by prokaryotic recombination with membrane hypertrophy, analogous to Gemmata obscuriglobus and other δ-proteobacteria with membrane-bounded nucleoids. Histone-coated DNA, protein-synthetic RNAs, amino-acylating, and other enzymes were contributed by the sulfidogen whereas most intracellular motility derives from the spirochete. From this redox syntrophy in anoxic and microoxic Proterozoic habitats LECA evolved. The nucleus originated by recombination of eu- and archaebacterial DNA that remained attached to eubacterial motility structures and became the microtubular cytoskeleton, including the mitotic apparatus. Direct LECA descendants include free-living archaeprotists in anoxic environments: archamoebae, metamonads, parabasalids, and some mammalian symbionts with mitosomes. LECA later acquired the fully aerobic Krebs cycle-oxidative phosphorylation-mitochondrial metabolism by integration of the protomitochondrion, a third α-proteobacterial symbiont from which the ancestors to most protoctists, all fungi, plants, and animals evolved. Secondarily anaerobic eukaryotes descended from LECA after integration of this oxygen-respiring eubacterium. Explanatory power and experimental predictions for molecular biology of the LECA concept are stated.
机译：我们在富含硫化物的环境中开发了厌氧但耐气螺旋体的真核细胞内运动系统起源的共生概念。最后的真核祖先（LECA）具有现存的考古学后裔：能动的有核细胞，带有Embden-Meyerhof糖酵解作用和底物水平的磷酸化作用，缺少成为线粒体的α-细菌共生体。具有硫化物的无壁古细菌（thermoplasmas）在附着有含耐气孔的螺旋体（真细菌）后，已经获得了通过硫化物进行游泳和调节O2耐受性的能力。类似于现存的硫同养生物（硫杜龙），硫化物氧化/减硫组合的稳定性提高，导致融合。由于原核重组与膜肥大一起进化出核，因此真细菌-古细菌共生成为永久性的，类似于Gemmata obscuriglobus和其他具有膜结合核苷的δ-变形细菌。亚硫酸盐原包裹着组蛋白包被的DNA，蛋白质合成的RNA，氨基酰化酶和其他酶，而大多数细胞内的运动性则来自螺旋体。从这种在缺氧和微缺氧的元古代生境中的氧化还原同质体中，进化出了LECA。细胞核是由正常细菌和古细菌DNA的重组产生的，该DNA仍附着在真细菌运动结构上，并成为包括有丝分裂装置在内的微管细胞骨架。 LECA的直接后代包括在缺氧环境中自由生活的考古学家：古细菌，metamonads，parabasalids和一些带有线粒体的哺乳动物共生体。 LECA后来通过整合线粒体（第三种α-蛋白质细菌共生体）而获得了完全有氧的Krebs循环-氧化磷酸化-线粒体代谢，其始祖是大多数人，所有真菌，植物和动物的祖先。第二，厌氧真核生物是从这种吸氧真细菌整合后的LECA衍生出来的。阐述了LECA概念的分子生物学解释力和实验预测。

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