PNAS:生物多细胞性是进化的关键因素
腾讯科学 · 2013/01/18
瑞士苏黎世、哥德堡大学研究人员发现蓝藻活动使地球大气充满了氧气,但后来的多细胞性演化是生物进化的关键因素。

据国外媒体报道,一项由瑞士苏黎世、哥德堡大学研究人员负责的研究表明,早在24亿年前的地球上,蓝藻的活动使得大气中充满了氧气,允许好氧生物的出现和进化。而今天发表于国家科学研究院的论文认为可通过模型重建来研究蓝藻对地球大气的影响。这些细菌在形态学上的变化是令人影响深刻的,可分布在不同的栖息环境中,其中包括了海洋、湖泊、土壤甚至是热液喷口,它们也是地球上最为古老的生物之一。但今天看来,对我们这个星球的生态系统而言,这并不是唯一重要的,而蓝藻的存在史也超过了20亿年。

缺少氧气和看似无法居住的地球开始慢慢聚集氧气,今天我们可以看到地球上存在多种多样的生物,然而有很少人了解到蓝藻谱系的演化方式,比如演化时间、蓝藻的起源等信息,蓝藻多样化和大气中突然增加的氧气之间可能存在相互作用。通过结合古老的化石和活体生物体基因,研究人员探索了多细胞重叠演化,了解到蓝藻细胞的多样化率与多细胞之间的显著变化。结果发现蓝藻在积累大气中氧气和多细胞形式演化过程中扮演了重要作用。

根据本项研究的主要作者贝蒂娜博士介绍:“起源于地球早期的蓝藻对我们星球的早期环境影响很大,可能帮助糟糕的行星环境得到改善,大量增加的蓝藻为随后大气中氧气占主导作用奠定了基础。”这项研究的另一个潜在方向认为生物多样性演变可以深刻改变地球环境,例如在全球变暖的背景下,环境变化对生物多样性构成了影响,研究人员下一个目标是更好地了解导致蓝藻进化的因素和演化结果。

Evolution of multicellularity coincided with increased diversification of cyanobacteria and the Great Oxidation Event

Bettina E. Schirrmeistera, Jurriaan M. de Vosb, Alexandre Antonellic, and Homayoun C. Bagheria

Cyanobacteria are among the most diverse prokaryotic phyla, with morphotypes ranging from unicellular to multicellular filamentous forms, including those able to terminally (i.e., irreversibly) differentiate in form and function. It has been suggested that cyanobacteria raised oxygen levels in the atmosphere around 2.45–2.32 billion y ago during the Great Oxidation Event (GOE), hence dramatically changing life on the planet. However, little is known about the temporal evolution of cyanobacterial lineages, and possible interplay between the origin of multicellularity, diversification of cyanobacteria, and the rise of atmospheric oxygen. We estimated divergence times of extant cyanobacterial lineages under Bayesian relaxed clocks for a dataset of 16S rRNA sequences representing the entire known diversity of this phylum. We tested whether the evolution of multicellularity overlaps with the GOE, and whether multicellularity is associated with significant shifts in diversification rates in cyanobacteria. Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE.

文献链接:http://www.pnas.org/content/early/2013/01/09/1209927110.abstract

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