Solar ultraviolet and the evolutionary history of cyanobacteria
Solar ultraviolet and the evolutionary history of cyanobacteria
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DOI：
10.1023/a:1006545303412
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发表时间：
1998-06-01
影响因子：
2
通讯作者：
Garcia-Pichel, F
中科院分区：
文献类型：
--
作者：
Garcia-Pichel, F
根据光生物学、进化论、古生物学、古环境和生理学的观点，提出了太阳紫外线辐射(波长在400 nm以下)在蓝藻生态和演化中的作用的时间进程，并将其分为三个主要阶段。在氧合光合作用出现之前的一个初始阶段，此时高环境通量的UVC(波长低于280 nm)和UVB(280-320 nm)可能会抑制原蓝藻发展大量种群的能力，或限制它们到UVR避难所。第二个阶段持续500-1500 Ma(百万年)，开始于真正放氧蓝藻的出现和在无氧大气下伴随而来的有氧(微)环境的形成。在这第二个阶段，紫外线的年龄，UVR的整体重要性肯定已经大幅增加，因为UVC和UVB的入射通量几乎保持不变，但另外，光谱中的UVA部分(320-400 nm)突然变得具有生物伤害性，在氧和UVR空间重合的地方一定形成了极具活性的氧物种。最后一个时期开始于大气的逐渐氧化和平流层臭氧层的形成。UVC引起的生理应激几乎消失，UVB的影响在很大程度上得到了减轻。支持这一动态的证据来自蓝藻和其他微生物之间生化紫外线防御机制的系统发育分布。利用浮游、沉积和陆地生境中紫外线辐射和氧气暴露的特定物理特征，探讨了在每个时期紫外线辐射对蓝藻生态分布的可能影响。
On the basis of photobiological, evolutionary, paleontological, paleoenvironmental and physiological arguments, a time course for the role of solar ultraviolet radiation (UVR, wavelengths below 400 nm) in the ecology and evolution of cyanobacteria is proposed in which three main periods can be distinguished. An initial stage, before the advent of oxygenic photosynthesis, when high environmental fluxes of UVC (wavelengths below 280 nm) and UVB (280-320 nm) may have depressed the ability of protocyanobacteria to develop large populations or restricted them to UVR refuges. A second stage lasting between 500 and 1500 Ma (million years), started with the appearance of true oxygen-evolving cyanobacteria and the concomitant formation of oxygenated (micro)environments under an oxygen free-atmosphere. In this second stage, the age of UV, the overall importance of UVR must have increased substantially, since the incident fluxes of UVC and UVB remained virtually unchanged, but additionally the UVA portion of the spectrum (320-400 nm) suddenly became biologically injurious and extremely reactive oxygen species must have formed wherever oxygen and UVR spatially coincided. The last period began with the gradual oxygenation of the atmosphere and the formation of the stratospheric ozone shield. The physiological stress due to UVC all but disappeared and the effects of UVB were reduced to a large extent. Evidence in support of this dynamics is drawn from the phylogenetic distribution of biochemical UV-defense mechanisms among cyanobacteria and other microorganisms. The specific physical characteristics of UVR and oxygen exposure in planktonic, sedimentary and terrestrial habitats are used to explore the plausible impact of UVR in each of the periods on the ecological distribution of cyanobacteria.