A Major Clade of Prokaryotes with Ancient Adaptations to Life on Land
A Major Clade of Prokaryotes with Ancient Adaptations to Life on Land
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DOI：
10.1093/molbev/msn247
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发表时间：
2009-02-01
影响因子：
10.7
通讯作者：
Hedges, S. Blair
中科院分区：
文献类型：
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作者：
Battistuzzi, Fabia U.;Hedges, S. Blair
原核生物的进化树通常定义已知的类和门，但很少就这些类群之间的关系达成一致。这归因于水平基因转移、序列变化的偏差和大的进化距离的影响。此外，原核生物门的高级进化枝很少得到生态学和细胞生物学信息的支持。尽管如此，随着使用复杂方法分析大量物种，共同模式开始出现。在这里，我们展示了来自系统发育、细胞学和环境数据的综合证据如何支持一个进化群体的存在，该进化群体似乎在地球历史早期就在陆地上拥有共同的祖先，并且包括三分之二的已知原核生物物种。该陆生进化枝（Terrabacteria）的成员包括蓝藻门、革兰氏阳性门（放线菌门和厚壁菌门）以及细胞壁结构与典型革兰氏阳性门和革兰氏阴性门不同的两个门（绿屈菌门和奇球菌-栖热菌门），它们具有重要的适应能力，例如对环境危害的抵抗力（例如， 干燥、紫外线辐射和高盐度）和产氧光合作用。此外，革兰氏阳性类群细胞壁的独特特性可能是为了响应陆地条件而进化的，这有助于许多物种的致病性。这些结果现在提出了一种可能性，即陆地适应在原核生物进化中发挥的作用可能比目前所理解的更大。
Evolutionary trees of prokaryotes usually define the known classes and phyla but less often agree on the relationships among those groups. This has been attributed to the effects of horizontal gene transfer, biases in sequence change, and large evolutionary distances. Furthermore, higher level clades of prokaryote phyla rarely are supported by information from ecology and cell biology. Nonetheless, common patterns are beginning to emerge as larger numbers of species are analyzed with sophisticated methods. Here, we show how combined evidence from phylogenetic, cytological, and environmental data support the existence of an evolutionary group that appears to have had a common ancestor on land early in Earth's history and includes two-thirds of known prokaryote species. Members of this terrestrial clade (Terrabacteria), which includes Cyanobacteria, the gram-positive phyla (Actinobacteria and Firmicutes), and two phyla with cell walls that differ structurally from typical gram-positive and gram-negative phyla (Chloroflexi and Deinococcus-Thermus), possess important adaptations such as resistance to environmental hazards (e.g., desiccation, ultraviolet radiation, and high salinity) and oxygenic photosynthesis. Moreover, the unique properties of the cell wall in gram-positive taxa, which likely evolved in response to terrestrial conditions, have contributed toward pathogenicity in many species. These results now leave open the possibility that terrestrial adaptations may have played a larger role in prokaryote evolution than currently understood.