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<p>Banded iron formations (BIF) were deposited abundantly between 2.7-2.4 Ga from iron- and silica-rich oceans, with cyanobacterial oxygen (O<sub>2</sub>) as a possible oxidant for Fe(II)<sub>(aq)</sub> oxidation and Fe(III) oxyhydroxide precipitation. However, toxic reactive oxygen species (ROS) from Fe(II)/O<sub>2</sub> interactions might have inhibited cyanobacterial growth, contributing to the delay between cyanobacterial evolution (&gt;3.0 Ga) and the Great Oxidation Event (2.5 Ga). Here, we explored the impact of Fe(II)<sub>(aq)</sub> and SiO<sub>2(aq)</sub> on <i>Synechococcus sp</i>. PCC 7002. High Fe(II)<sub>(aq)</sub> ( &gt; 500 µM) increased ROS formation, but elevated SiO<sub>2(aq)</sub> (2200 µM) suppressed ROS formation, promoting growth and O<sub>2</sub> production. Diel light cycles further reduced ROS formation compared to continuous illumination. Modelling O<sub>2</sub> distribution based on experimental rates revealed oxygenated surface waters at relevant upwelling rates. Together, our results indicate that high SiO<sub>2(aq)</sub> and day-night-light cycles in Archean oceans mitigated ROS stress, enabling cyanobacterial proliferation and enhancing their role in Earth’s oxygenation and BIF deposition.</p>

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Survival of cyanobacteria and mitigation of Fe(II) toxicity effects in a silica-rich Archean ocean

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月21日

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  • Carolin L. Dreher,
  • Olaf A. Cirpka,
  • Manuel Schad,
  • Kurt O. Konhauser,
  • Andreas Kappler

摘要

Banded iron formations (BIF) were deposited abundantly between 2.7-2.4 Ga from iron- and silica-rich oceans, with cyanobacterial oxygen (O2) as a possible oxidant for Fe(II)(aq) oxidation and Fe(III) oxyhydroxide precipitation. However, toxic reactive oxygen species (ROS) from Fe(II)/O2 interactions might have inhibited cyanobacterial growth, contributing to the delay between cyanobacterial evolution (>3.0 Ga) and the Great Oxidation Event (2.5 Ga). Here, we explored the impact of Fe(II)(aq) and SiO2(aq) on Synechococcus sp. PCC 7002. High Fe(II)(aq) ( > 500 µM) increased ROS formation, but elevated SiO2(aq) (2200 µM) suppressed ROS formation, promoting growth and O2 production. Diel light cycles further reduced ROS formation compared to continuous illumination. Modelling O2 distribution based on experimental rates revealed oxygenated surface waters at relevant upwelling rates. Together, our results indicate that high SiO2(aq) and day-night-light cycles in Archean oceans mitigated ROS stress, enabling cyanobacterial proliferation and enhancing their role in Earth’s oxygenation and BIF deposition.