Reactive Fe(III) minerals can influence methane (CH₄) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH₄ oxidation. The balance between Fe(III) reduction, methanogenesis, and CH₄ oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH₄ fluxes to the atmosphere, thereby regulating the capacity for CH₄ to warm the early Earth under the Faint Young Sun. We studied CH₄ and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total). Iron reduction, methanogenesis, CH₄ oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH₄ production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)‐dependent CH₄ oxidation, although some incubations displayed CH₄‐stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)‐reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH₄ as a greenhouse gas throughout the first half of Earth history.

中文翻译：

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不断变化的微生物群落在铁质沉积物孵化过程中维持了多年的铁还原和产甲烷作用。


活性 Fe(III) 矿物可通过抑制微生物产甲烷作用或刺激厌氧 CH ₄氧化来影响甲烷 (CH ₄ ) 排放。铁质太古宙和古元古代海洋中 Fe(III) 还原、产甲烷作用和 CH ₄氧化之间的平衡将控制 CH ₄进入大气的通量，从而调节 CH ₄在微弱的年轻太阳下使早期地球变暖的能力。我们研究了来自印度尼西亚马塔诺湖的含铁沉积物缺氧培养中的 CH ₄和 Fe 循环，连续三次转移（总共 500 天）。在用水铁矿或针铁矿修正的处理中监测铁还原、产甲烷、CH ₄氧化和微生物分类。经过三次稀释后，Fe(III) 还原仅在装有水铁矿的瓶子中持续存在。在针铁矿存在下观察到 CH ₄产量增加，突出了反应性 Fe(III) 氧化物抑制产甲烷作用的潜力。在培养基中补充氢、镍和硒并不能刺激产甲烷作用。虽然一些孵育显示 CH ₄刺激 Fe(III) 还原，但 Fe(III) 依赖性 CH ₄氧化的证据有限。 16S rRNA 谱在富集过程中不断变化，在所有处理中，脱硫单胞菌目的未分类成员最终占主导地位。在孵化过程中，微生物多样性显着下降，水铁矿和针铁矿改良剂之间存在细微差别。 这些结果表明，Fe(III) 氧化物矿物学和电子供体的可用性可能导致含铁海洋沉积物中 Fe(III) 还原微生物群落和产甲烷微生物群落的空间分离，这可能解释了 CH ₄作为温室气体在整个海洋中的持续存在。地球历史的前半部分。