Protection of phototrophic iron(II)-oxidizing bacteria from UV irradiation by biogenic iron(III) minerals: Implications for early Archean banded iron formation
Protection of phototrophic iron(II)-oxidizing bacteria from UV irradiation by biogenic iron(III) minerals: Implications for early Archean banded iron formation
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DOI：
10.1130/g37095.1
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发表时间：
2015-12-01
期刊：
影响因子：
5.8
通讯作者：
Kappler, Andreas
中科院分区：
文献类型：
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作者：
Gauger, Tina;Konhauser, Kurt;Kappler, Andreas
在太古代地球（4.0-2.5 Ga），缺乏保护性的臭氧层意味着有害的紫外线辐射（UVR）几乎没有衰减地到达地表。为了生存，原始的光合细菌需要防止紫外线对其DNA造成损伤的策略。在那个时候，一小部分的光合细胞可能是无氧光合作用，氧化溶解铁（II）的铁（III）在他们的新陈代谢。它们代谢的结果很可能是条带状铁建造沉积的铁矿物前体。虽然Fe（III）（oxyhydr）氧化物矿物质吸收紫外线辐射，同时仍然传输更高的波长，但不知道Fe（II）氧化剂产生的矿物质是否可以作为原位紫外线防晒剂。在这里，我们表明，缺氧的光养Fe（II）氧化剂沼泽红细菌TIE-1菌株和氧化亚铁红细菌SW 2菌株形成纳米级的颗粒松散地附着在细胞表面的水铁矿。这些生物源Fe（III）矿物质被证明可以保护细菌免受紫外线C照射，而在不存在Fe（II）的情况下生长的细胞由于DNA损伤而显示出细胞活力下降。重要的是，这项研究意味着原始的Fe（II）氧化细菌能够产生自己的紫外线屏障，使它们能够生活在古代海洋的浅水区。
On the Archean Earth (4.0-2.5 Ga) the lack of a protective ozone layer meant that harmful ultraviolet radiation (UVR) reached the surface almost unattenuated. For survival, primitive photosynthetic bacteria would have required strategies preventing UV-induced damage to their DNA. At that time, a fraction of the planktonic cells were likely anoxygenic photosynthesizers that oxidized dissolved Fe(II) to Fe(III) during their metabolism. The result of their metabolism was most likely the ferric mineral precursors for the deposition of banded iron formations. Although Fe(III) (oxyhydr) oxide minerals absorb UV radiation while still transmitting higher wavelengths, it is unknown whether minerals produced by Fe(II) oxidizers could have acted as an in situ UVR sunscreen. Here we demonstrate that the anoxygenic phototrophic Fe(II) oxidizers Rhodopseudomonas palustris strain TIE-1 and Rhodobacter ferrooxidans strain SW2 form nanometer-sized grains of ferrihydrite that are loosely attached to the cell surfaces. These biogenic Fe(III) minerals were shown to protect the bacteria from UV-C irradiation, while cells grown in the absence of Fe(II) displayed diminished cell viability as a consequence of damage to their DNA. Importantly, this study implies that primitive Fe(II)oxidizing bacteria would have been able to produce their own UV screen, enabling them to live in the shallow photic zone of ancient oceans.