The evolutionary diversification of cyanobacteria: Molecular-phylogenetic and paleontological perspectives
The evolutionary diversification of cyanobacteria: Molecular-phylogenetic and paleontological perspectives
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DOI：
10.1073/pnas.0600999103
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发表时间：
2006-04-04
影响因子：
11.1
通讯作者：
Ohno, T
中科院分区：
文献类型：
--
作者：
Tomitani, A;Knoll, AH;Ohno, T
蓝藻在地球历史上扮演了重要的角色，作为主要的生产者和大气氧气的最终来源。然而，迄今为止，该集团如何以及何时实现多元化仍不清楚。在这里，我们结合联合收割机分子系统发育和古生物学的研究，阐明早期蓝藻多样化的模式和时间。对分布在16个属中的20种蓝细菌菌株的16 S rRNA、rbcL和hetR基因进行了测序，特别注意代表丝状分类群的已知多样性。与大多数其他细菌不同，一些丝状蓝藻进化出一定程度的细胞分化，产生专门的固氮细胞（异形胞）和能够承受环境压力的休眠细胞（动细胞）。系统发育分析支持的假设，蓝细菌的细胞分化能力是单系的，和地质记录提供了这支起源的上限和下限。在西伯利亚、中国和澳大利亚的1,650- 1,400百万年（Ma）的燧石中发现了化石akinetes，而在西非的大约2,100百万年（Ma）的燧石中保存着可能是已知最早的akinetes。地球化学证据表明，氧首先达到的水平，将损害固氮（因此选择异形胞分化）2，450 - 2，320 Ma。综合系统发育分析和地质数据，我们认为，蓝细菌的细胞分化标记的分支分歧一次之间的2,450和2,100马，提供了一个内部的细菌校准点的分子进化研究在早期生物。
Cyanobacteria have played a significant role in Earth history as primary producers and the ultimate source of atmospheric oxygen. To date, however, how and when the group diversified has remained unclear. Here, we combine molecular phylogenetic and paleontological studies to elucidate the pattern and timing of early cyanobacterial diversification. 16S rRNA, rbcL, and hetR genes were sequenced from 20 cyanobacterial strains distributed among 16 genera, with particular care taken to represent the known diversity of filamentous taxa. Unlike most other bacteria, some filamentous cyanobacteria evolved a degree of cell differentiation, producing both specialized cells for nitrogen fixation (heterocysts) and resting cells able to endure environmental stress (akinetes). Phylogenetic analyses support the hypothesis that cyanobacteria capable of cell differentiation are monophyletic, and the geological record provides both upper and lower bounds on the origin of this clade. Fossil alkinetes have been identified in 1,650- to 1,400-mega-annum (Ma) cherts from Siberia, China, and Australia, and what may be the earliest known akinetes are preserved in approximate to 2,100-Ma chert from West Africa. Geochemical evidence suggests that oxygen first reached levels that would compromise nitrogen fixation (and hence select for heterocyst differentiation) 2,450-2,320 Ma. Integrating phylogenetic analyses and geological data, we suggest that the clade of cyanobacteria marked by cell differentiation diverged once between 2,450 and 2,100 Ma, providing an internal bacterial calibration point for studies of molecular evolution in early organisms.