The Influence of Reactive Oxygen Species on Local Redox Conditions in Oxygenated Natural Waters
The Influence of Reactive Oxygen Species on Local Redox Conditions in Oxygenated Natural Waters
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DOI：
10.3389/feart.2016.00096
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发表时间：
2016-11
影响因子：
2.9
通讯作者：
A. Rose
中科院分区：
文献类型：
--
作者：
A. Rose
天然水体的氧化还原条件对生物地球化学过程和许多生态系统功能具有根本的控制作用。虽然在地质时间尺度上，双氧/水氧化还原偶控制着含氧水生环境中的氧化还原热力学，但在许多生物地球化学过程发生的更短时间尺度上，它在细胞外环境中是动力学惰性的。相反，这些时间尺度上的电子转移过程主要是由相对较少的微量金属和稳定自由基（包括活性氧超氧化物）介导的。这些过程具有重要的生物地球化学意义，因为许多这些化学物质是稀缺的营养物质，但在高浓度时也可能有毒。此外，它们的生物利用度和潜在毒性通常受其氧化还原状态的强烈影响。在本文中，我研究了氧化天然水中的氧化还原条件在多大程度上反映在易挥发的氧化还原活性化合物的氧化还原状态中，这些化合物容易与双氧/超氧氧化还原偶对交换电子，并且可能彼此交换电子。此外，我提出了一个假设，即在生物地球化学重要的时间尺度上，双氧/超氧和超氧/过氧化氢氧化还原对含氧天然水中局部氧化还原条件的相对重要性施加了控制。鉴于最近发现多种生物广泛产生细胞外超氧化物，这表明存在一种基本机制，使生物在含氧天然水域的细胞外环境中严格调节局部氧化还原条件。
Redox conditions in natural waters are a fundamental control on biogeochemical processes and ultimately many ecosystem functions. While the dioxygen/water redox couple controls redox thermodynamics in oxygenated aquatic environments on geological timescales, it is kinetically inert in the extracellular environment on the much shorter timescales on which many biogeochemical processes occur. Instead, electron transfer processes on these timescales are primarily mediated by a relatively small group of trace metals and stable radicals, including the reactive oxygen species superoxide. Such processes are of critical biogeochemical importance because many of these chemical species are scarce nutrients, but may also be toxic at high concentrations. Furthermore, their bioavailability and potentially toxicity is typically strongly influenced by their redox state. In this paper, I examine to what extent redox conditions in oxygenated natural waters are expected to be reflected in the redox states of labile redox-active compounds that readily exchange electrons with the dioxygen/superoxide redox couple, and potentially with each other. Additionally, I present the hypothesis that that the relative importance of the dioxygen/superoxide and superoxide/hydrogen peroxide redox couples exerts a governing control on local redox conditions in oxygenated natural waters on biogeochemically important timescales. Given the recent discovery of widespread extracellular superoxide production by a diverse range of organisms, this suggests the existence of a fundamental mechanism for organisms to tightly regulate local redox conditions in their extracellular environment in oxygenated natural waters.