Higher-level classification of the Archaea: evolution of methanogenesis and methanogens
Higher-level classification of the Archaea: evolution of methanogenesis and methanogens
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DOI：
10.1155/2005/859728
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发表时间：
2005-05-05
期刊：
影响因子：
2.4
通讯作者：
Boucher, Yan
中科院分区：
文献类型：
--
作者：
Bapteste, Eric;Brochier, Celine;Boucher, Yan
我们使用系统发育的方法来分析甲烷和产甲烷菌的进化。我们发现，23垂直传输的核糖体蛋白不支持产甲烷菌的单系性，并建议，而不是有两个遥远的相关组现存的古生菌产生甲烷，我们命名为I类和II类。基于这一发现，我们随后调查的独特性的起源甲烷通过研究的酶和蛋白质合成其特定的辅酶。我们的结论是，氢营养甲烷在进化过程中只出现一次。参与二氧化碳（CO2）的产甲烷还原的七个核心步骤的基因在产甲烷菌中普遍存在，并且具有共同的历史。这表明，虽然现存的产甲烷菌从各种底物（CO2，甲酸盐，乙酸盐，甲基化的C-1化合物）产生甲烷，这些古细菌有一个保守的酶的核心，经历了很少的进化变化。此外，产甲烷酶的核心似乎（作为一个整体）起源于所有产甲烷菌的最后祖先，似乎没有水平传播到其他生物体或I类和II类成员之间。对甲烷生成的独特和祖先形式的观察表明，它被保存在两个独立的谱系中，具有一些专门化或增加代谢灵活性的情况。它可能在盐杆菌目、热胞浆菌目和古菌目中丢失。鉴于化石证据甲烷生成可以追溯到28亿年前，这一过程的独特起源使产甲烷古菌成为一个非常古老的分类群。
We used a phylogenetic approach to analyze the evolution of methanogenesis and methanogens. We show that 23 vertically transmitted ribosomal proteins do not support the monophyly of methanogens, and propose instead that there are two distantly related groups of extant archaea that produce methane, which we have named Class I and Class II. Based on this finding, we subsequently investigated the uniqueness of the origin of methanogenesis by studying both the enzymes of methanogenesis and the proteins that synthesize its specific coenzymes. We conclude that hydrogenotrophic methanogenesis appeared only once during evolution. Genes involved in the seven central steps of the methanogenic reduction of carbon dioxide (CO2) are ubiquitous in methanogens and share a common history. This suggests that, although extant methanogens produce methane from various substrates (CO2, formate, acetate, methylated C-1 compounds), these archaea have a core of conserved enzymes that have undergone little evolutionary change. Furthermore, this core of methanogenesis enzymes seems to originate (as a whole) from the last ancestor of all methanogens and does not appear to have been horizontally transmitted to other organisms or between members of Class I and Class II. The observation of a unique and ancestral form of methanogenesis suggests that it was preserved in two independent lineages, with some instances of specialization or added metabolic flexibility. It was likely lost in the Halobacteriales, Thermoplasmatales and Archaeoglobales. Given that fossil evidence for methanogenesis dates back 2.8 billion years, a unique origin of this process makes the methanogenic archaea a very ancient taxon.