Abstract Life most likely developed under hyperthermic and anaerobic conditions in close vicinity to a stable geochemical source of energy. Epitomizing this conception, the first cells may have arisen in submarine hydrothermal vents in the middle of a gradient established by the hot and alkaline hydrothermal fluid and the cooler and more acidic water of the ocean. To enable their escape from this energy-providing gradient layer, the early cells must have overcome a whole series of obstacles. Beyond the loss of their energy source, the early cells had to adapt to a loss of external iron-sulfur catalysis as well as to a formidable temperature drop. The developed solutions to these two problems seem to have followed the principle of maximum parsimony: Cysteine was introduced into the genetic code to anchor iron-sulfur clusters, and fatty acid unsaturation was installed to maintain lipid bilayer viscosity. Unfortunately, both solutions turned out to be detrimental when the biosphere became more oxidizing after the evolution of oxygenic photosynthesis. To render cysteine thiol groups and fatty acid unsaturation compatible with life under oxygen, numerous counter-adaptations were required including the advent of glutathione and the addition of the four latest amino acids (methionine, tyrosine, tryptophan, selenocysteine) to the genetic code. In view of the continued diversification of derived antioxidant mechanisms, it appears that modern life still struggles with the initially developed strategies to escape from its hydrothermal birthplace. Only archaea may have found a more durable solution by entirely exchanging their lipid bilayer components and rigorously restricting cysteine usage.

中文翻译：

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半胱氨酸、谷胱甘肽和新的遗传密码：原始细胞的生化适应，以扩散到开放水域并在生物圈氧合中存活

摘要 生命最有可能在靠近稳定地球化学能源的高温和厌氧条件下发展起来。作为这一概念的缩影，第一个细胞可能出现在海底热液喷口中，该热液喷口位于由热的碱性热液流体和较冷、酸性更强的海洋形成的梯度中间。为了摆脱这个提供能量的梯度层，早期细胞必须克服一系列障碍。除了能量来源的损失之外，早期的电池还必须适应外部铁硫催化的损失以及巨大的温度下降。这两个问题的已开发解决方案似乎遵循了最大简约原则：将半胱氨酸引入遗传密码以锚定铁硫簇，并且安装了不饱和脂肪酸以保持脂双层粘度。不幸的是，当生物圈在含氧光合作用进化后变得更加氧化时，这两种解决方案都被证明是有害的。为了使半胱氨酸硫醇基团和脂肪酸不饱和度与氧气下的生命相容，需要进行许多逆适应，包括谷胱甘肽的出现和向遗传密码中添加四种最新的氨基酸（蛋氨酸、酪氨酸、色氨酸、硒代半胱氨酸）。鉴于衍生抗氧化机制的持续多样化，现代生活似乎仍在与最初制定的逃离其热液发源地的策略作斗争。