細胞膜、前駆細胞、普遍的な祖先（ルカ）の起源

細菌と古細菌に存在する細胞膜の多様性が、最後の普遍的な共通祖先（LUCA）の細胞性の進化によって到達する段階に対して持つことの結果を分析します。細菌と古細菌の膜がどのようにルカに分布したかに関係なく、出現すると思われる結論は常に同じです。つまり、ルカはジェノットではなく隔離性であった可能性が高いです。確かに、ルカが両方のタイプの膜をホストした場合、これはルカ自体が前角度であることを意味する移行状態でした。言い換えれば、2種類の膜は明らかに細菌とArchaeaの膜の分離を隔離しなければならなかった。この分離は、細胞段階では予想されない大きな変化を暗示するだろうが、前胞の標準であることを暗示している。代わりに、ルカが1つのタイプの膜、たとえば古細菌の膜のみをホストしていた場合、他のタイプの膜の進化 - おそらく細菌の祖先である - は、そのような後期起源が正確に前進的なルカを暗示します。当時、根本的で深遠な遺伝的特性を伴うため、まだ急速かつ進歩的な進化の表現のように思えます。したがって、前進段階を反映する必要があります。最後に、ルカが膜を欠いていた場合、2つのタイプの膜の後期起源 - アルカエアの祖先と細菌の祖先 - は、典型的な迅速で進歩的な進化の明確な表現のように思われます。断層の。実際、これは、たとえば、2つの細胞膜に関連するすべてのメカニズムと機能がまだ進化しなければならなかったことを意味します。断層。したがって、ルカは、ルカが代わりに細胞性の進化段階に到達したという仮説を支持する強い議論がないため、おそらく後継者であった可能性が高い。

I analyse the consequences that the diversity of cell membranes present in bacteria and archaea would have for the stage reached by the evolution of cellularity in the Last Universal Common Ancestor (LUCA). Regardless of how the bacterial and archaeal membranes were distributed in the LUCA, the conclusion that would seem to emerge is always the same. That is to say, it is more likely that LUCA was a progenote rather than a genote. Indeed, if LUCA hosted both types of membranes then this would have been a transitional condition which would imply, in itself, that LUCA was a progenote. In other words, the two types of membranes evidently had to segregate in that of bacteria and that of archaea, and this segregation would imply enormous changes not expected for a cellular stage but the norm for that of progenote. Instead, in the case in which LUCA hosted only one type of membrane, for example that of archaea, then the evolution of the other type of membrane - presumably in the ancestor of bacteria - would imply a progenotic LUCA precisely because such a late origin would seem be an expression, at that time, of a still rapid and progressive evolution because it involves a fundamental and profound genetic trait, and should therefore reflect the progenotic stage. Finally, in the event that LUCA had been devoid of a membrane, then the late origin of the two types of membranes - in the ancestor of archaea and in that of bacteria - would seem to be a clear expression of a rapid and progressive evolution typical of progenote. Indeed, this would imply, for example, that all mechanisms and functions associated with the two cell membranes still had to evolve which would express the progenotic stage precisely because it would seem to be an evolution still in progress, and therefore typical of the stage of progenote. Therefore, LUCA was most likely a progenote also because there would be no strong arguments in favour of the hypothesis that LUCA had instead reached the evolutionary stage of cellularity.