The Great Oxidation Event (GOE) was a rapid accumulation of oxygen in the atmosphere as a result of the photosynthetic activity of cyanobacteria. This accumulation reflected the pervasiveness of O₂ on the planet's surface, indicating that cyanobacteria had become ecologically successful in Archean oceans. Micromolar concentrations of Fe²⁺ in Archean oceans would have reacted with hydrogen peroxide, a byproduct of oxygenic photosynthesis, to produce hydroxyl radicals, which cause cellular damage. Yet, cyanobacteria colonized Archean oceans extensively enough to oxygenate the atmosphere, which likely required protection mechanisms against the negative impacts of hydroxyl radical production in Fe²⁺-rich seas. We identify several factors that could have acted to protect early cyanobacteria from the impacts of hydroxyl radical production and hypothesize that microbial cooperation may have played an important role in protecting cyanobacteria from Fe²⁺ toxicity before the GOE. We found that several strains of facultative anaerobic heterotrophic bacteria (Shewanella) with ROS defence mechanisms increase the fitness of cyanobacteria (Synechococcus) in ferruginous waters. Shewanella species with manganese transporters provided the most protection. Our results suggest that a tightly regulated response to prevent Fe²⁺ toxicity could have been important for the colonization of ancient ferruginous oceans, particularly in the presence of high manganese concentrations and may expand the upper bound for tolerable Fe²⁺ concentrations for cyanobacteria.

中文翻译：

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微生物助手让蓝藻在含铁水中茁壮成长

大氧化事件（GOE）是由于蓝藻的光合作用活动导致大气中氧气的快速积累。这种积累反映了O ₂在地球表面的普遍存在，表明蓝藻在太古宙海洋中已经在生态上取得了成功。太古宙海洋中微摩尔浓度的 Fe ²⁺会与过氧化氢（含氧光合作用的副产品）反应产生羟基自由基，从而导致细胞损伤。然而，蓝细菌在太古宙大范围内定殖足以为大气增氧，这可能需要保护机制来抵御 Fe ^{2+中羟基自由基产生的负面影响}- 丰富的海洋。我们确定了几个可能起到保护早期蓝藻免受羟基自由基产生影响的因素，并假设微生物合作可能在 GOE 之前保护蓝藻免受 Fe ^{2+毒性方面发挥了重要作用。}我们发现几种具有 ROS 防御机制的兼性厌氧异养细菌 ( Shewanella ) 菌株增加了蓝藻 ( Synechococcus ) 在含铁水中的适应性。具有锰转运蛋白的Shewanella物种提供了最大的保护。我们的结果表明，防止 Fe ^{2+受到严格调控的反应}毒性对于古代含铁海洋的定殖可能很重要，特别是在锰浓度高的情况下，并且可能扩大蓝藻可耐受的 Fe ²⁺浓度的上限。