Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen
Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen
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DOI：
10.1073/pnas.1912313117
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发表时间：
2020-02-18
影响因子：
11.1
通讯作者：
Hansel, Colleen M.
中科院分区：
文献类型：
--
作者：
Sutherland, Kevin M.;Wankel, Scott D.;Hansel, Colleen M.
自光合作用演化以来，海洋中分子氧的源汇平衡极大地影响着地球大气的组成，从而对地球气候和地表（次）氧化还原状态产生重要影响。海洋氧收支的标准源和汇项包括光合作用、呼吸作用、光呼吸作用、Mehler反应和其他较小的项。然而，最近的进展，在了解神秘的氧循环，即无处不在的单电子还原O-2超氧化物的细胞外的微生物，仍然是未开发的全球氧动力学的潜在球员。在这里，我们表明，黑暗的细胞外超氧化物的海洋微生物生产代表了以前未被考虑的全球氧通量和汇的幅度与其他关键词。我们估计，细胞外超氧化物的产生代表了一个总的氧汇，包括约三分之一的海洋总氧生产，和净氧汇的15至50%。我们进一步证明，这总的海洋黑暗的细胞外超氧化物通量是一致的，在海洋环境中的超氧化物的浓度。这些研究结果强调了丰富的海洋来源的活性氧物种和一个复杂的和动态的氧循环，其中氧的消耗和相应的碳氧化不一定局限于细胞膜或专门与呼吸。海洋氧循环的这一修订模型最终将允许初级生产和呼吸的估计之间的更大的和解，并在海洋中的氧化还原循环的更大的机械理解。
The balance between sources and sinks of molecular oxygen in the oceans has greatly impacted the composition of Earth's atmosphere since the evolution of oxygenic photosynthesis, thereby exerting key influence on Earth's climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine oxygen budget include photosynthesis, respiration, photo-respiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic oxygen cycling, namely the ubiquitous one-electron reduction of O-2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross oxygen sink comprising about a third of marine gross oxygen production, and a net oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive oxygen species and a complex and dynamic oxygen cycle in which oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine oxygen cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.