The Influence of Extracellular Superoxide on Iron Redox Chemistry and Bioavailability to Aquatic Microorganisms

Rose, Arthur W.

doi:10.3389/fmicb.2012.00124

Cited by 64 publications

(81 citation statements)

References 136 publications

(208 reference statements)

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“…This could be explained by the fact that Mn 2ϩ has a higher reaction rate with superoxide than does iodide at a nearneutral pH (36). In addition to Mn 2ϩ , other metals, such as iron and copper ions, also exhibit higher reaction rates with superoxide than with iodide (36,39). In terrestrial environments (i.e., soils or groundwater), which typically contain higher concentrations of Mn 2ϩ or Fe ions (M to mM range) than iodide (low M), iodide oxidation mediated by superoxide may not be a significant pathway in bulk pore water.…”

Section: Discussionmentioning

confidence: 94%

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

Daniel

Creeley

et al. 2014

Appl Environ Microbiol

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The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I ؊ ), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O 2 ؊ ). In the absence of Mn 2؉ , Roseobacter sp. AzwK-3b cultures oxidized ϳ90% of the provided iodide (10 M) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments.

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Section: Discussionmentioning

confidence: 94%

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

Daniel

Creeley

et al. 2014

Appl Environ Microbiol

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“…23,24 As demonstrated previously, superoxide produced from KO 2 25,26 or photoirradiated natural organic matter 27 can also reduce Ag + into AgNPs. Therefore, it is reasonable that superoxide bioproduced by microorganisms could reduce Ag + into AgNPs.…”

Section: ■ Introductionmentioning

confidence: 88%

“…It was reported that superoxide can be produced by bacteria and fungi. [19][20][21]23,24 Here, for the first time, we demonstrated the production of superoxide by F. oxysporum by using continuous flow CL (Figure 2). No CL signal was observed when only F.…”

Section: Environmental Science and Technology Lettersmentioning

confidence: 99%

Superoxide-Mediated Extracellular Biosynthesis of Silver Nanoparticles by the Fungus Fusarium oxysporum

Yin

Xiao-ya

et al. 2016

Environ. Sci. Technol. Lett.

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The biosynthesis of silver nanoparticles (AgNPs) by microorganisms has become a hot topic in recent years, although its mechanism is still not well understood. Here we report the extracellular biosynthesis of AgNPs by the fungus Fusarium oxysporum through a superoxide-dependent mechanism. Reduction of Ag + to AgNPs in the extracellular region of F. oxysporum was verified by transmission electron microscopy, while the superoxide produced extracellularly by F. oxysporum was evidenced by chemiluminescence. We further demonstrated that the biosynthesis of AgNPs was inhibited by a superoxide scavenger or the inhibitor of NADH oxidases, and the addition of NADH significantly improved the formation of AgNPs. These results demonstrated that, for the first time, the fungus F. oxysporum can mediate the synthesis of AgNPs through the enzymatic generation of extracellular superoxide, which is helpful in understanding the biosynthesis of AgNPs and the biomineralization and transformation of silver and other metals or metalloids.

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“…The ability of O − 2 to influence the bioavailability of Fe in oxygenated waters by mediating its redox cycling has already been demonstrated under a range of scenarios (Kustka et al, 2005;Garg et al, 2007;Rose, 2012). Biologically produced extracellular O − 2 has also been shown to drive redox cycling of Mn in fungi (Hansel et al, 2012) and bacteria (Learman et al, 2011) under oxygenated conditions.…”

Section: Importance Of Ros For Local Redox Chemistry In Oxygenated Namentioning

confidence: 98%

The Influence of Reactive Oxygen Species on Local Redox Conditions in Oxygenated Natural Waters

Rose

2016

Front. Earth Sci.

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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 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.

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The Influence of Extracellular Superoxide on Iron Redox Chemistry and Bioavailability to Aquatic Microorganisms

Cited by 64 publications

References 136 publications

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

Superoxide-Mediated Extracellular Biosynthesis of Silver Nanoparticles by the Fungus Fusarium oxysporum

The Influence of Reactive Oxygen Species on Local Redox Conditions in Oxygenated Natural Waters

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