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    Gauger, Tina Konhauser, Kurt and Kappler, Andreas 2016. Protection of Nitrate-Reducing Fe(II)-Oxidizing Bacteria from UV Radiation by Biogenic Fe(III) Minerals. Astrobiology, Vol. 16, Issue. 4, p. 301.

    Figueredo, Federico Cortón, Eduardo and Abrevaya, Ximena C. 2015. In SituSearch for Extraterrestrial Life: A Microbial Fuel Cell–Based Sensor for the Detection of Photosynthetic Metabolism. Astrobiology, Vol. 15, Issue. 9, p. 717.

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    Stromberg, J. M. Applin, D. M. Cloutis, E. A. Rice, M. Berard, G. and Mann, P. 2014. The persistence of a chlorophyll spectral biosignature from Martian evaporite and spring analogues under Mars-like conditions. International Journal of Astrobiology, Vol. 13, Issue. 03, p. 203.

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    Burchell, M.J. 2010. The special issue devoted to papers from the fourth Astrobiology Society of Britain Conference, Royal Holloway, 2010. International Journal of Astrobiology, Vol. 9, Issue. 04, p. 191.

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    Cockell, C. S and Raven, J. A 2007. Ozone and life on the Archaean Earth. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 365, Issue. 1856, p. 1889.

  • International Journal of Astrobiology, Volume 5, Issue 1
  • January 2006, pp. 1-12

Nanophase iron oxides as a key ultraviolet sunscreen for ancient photosynthetic microbes

  • Janice L. Bishop (a1) (a2), Stephanie K. Louris (a3), Dana A. Rogoff (a1) (a3) and Lynn J. Rothschild (a3) (a4)
  • DOI:
  • Published online: 04 July 2006

We propose that nanophase iron-oxide-bearing materials provided important niches for ancient photosynthetic microbes on the Earth that ultimately led to the oxygenation of the Earth's atmosphere and the formation of iron-oxide deposits. Atmospheric oxygen and ozone attenuate ultraviolet radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose early and played a critical role in subsequent evolution. Of primary importance was protection below 290 nm, where peak nucleic acid (~260 nm) and protein (~280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal ultraviolet radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Furthermore, they were available in early environments, and are synthesized by many organisms. Based on experiments using nanophase ferric oxide/oxyhydroxide minerals as a sunscreen for photosynthetic microbes, we suggest that iron, an abundant element widely used in biological mechanisms, may have provided the protection that early organisms needed in order to be able to use photosynthetically active radiation while being protected from ultraviolet-induced damage. The results of this study are broadly applicable to astrobiology because of the abundance of iron in other potentially habitable bodies and the evolutionary pressure to utilize solar radiation when available as an energy source. This model could apply to a potential life form on Mars or other bodies where liquid water and ultraviolet radiation could have been present at significant levels. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the photosynthetic organisms, Euglena sp. and Chlamydomonas reinhardtii, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides.

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International Journal of Astrobiology
  • ISSN: 1473-5504
  • EISSN: 1475-3006
  • URL: /core/journals/international-journal-of-astrobiology
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