Abiotic oxidation of Fe(<scp>II</scp>) by reactive nitrogen species in cultures of the nitrate‐reducing Fe(<scp>II</scp>) oxidizer <i><scp>A</scp>cidovorax</i> sp. BoFeN1 – questioning the existence of enzymatic Fe(<scp>II</scp>) oxidation

Klueglein, Nicole; Kappler, Andreas

doi:10.1111/gbi.12019

Cited by 230 publications

(247 citation statements)

References 64 publications

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“…Minerals were recorded using their reflection signal of the 488-nm laser. [Similar Fe(II) oxidation rates for strain BoFeN1 and strain 2002 were published before (11,31).] Although the four strains showed very similar Fe(II) oxidation trends over time, nitrate reduction and nitrite accumulation differed slightly between the strains.…”

Section: Methodssupporting

confidence: 60%

“…2 HNO → N 2 O↑ ϩH 2 O (5) In a recent study (31), we demonstrated experimentally that reactive nitrite, which is produced, for example, by strain BoFeN1 during nitrate reduction with electrons from acetate oxidation, plays a major role in abiotic Fe(II) oxidation in these cultures. This raises the question of whether the strains isolated originally as nitrate-reducing Fe(II) oxidizers have a specific enzymatic machinery for Fe(II) oxidation at all, or whether at least some if not all of the observed Fe(II) oxidation is abiotically driven.…”

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confidence: 99%

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Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

Klueglein

Zeitvogel

Stierhof

et al. 2014

Appl Environ Microbiol

183

239

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Section: Methodssupporting

confidence: 60%

mentioning

confidence: 99%

Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

Klueglein

Zeitvogel

Stierhof

et al. 2014

Appl Environ Microbiol

183

239

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“…For these mixotrophic strains, it is not yet known whether Fe(II) oxidation is just a chemical side reaction with nitrite, which is produced during heterotrophic denitrification (26,27), or if it is an enzymatic reaction from which the bacteria can gain energy. Interestingly, Fe(II) oxidation seems to be a universal ability of all NO 3 Ϫ -reducing bacteria when an organic substrate is provided (28).…”

mentioning

confidence: 99%

Coexistence of Microaerophilic, Nitrate-Reducing, and Phototrophic Fe(II) Oxidizers and Fe(III) Reducers in Coastal Marine Sediment

Laufer

Nordhoff

Røy

et al. 2016

Appl Environ Microbiol

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Iron is abundant in sediments, where it can be biogeochemically cycled between its divalent and trivalent redox states. The neutrophilic microbiological Fe cycle involves Fe(III)-reducing and three different physiological groups of Fe(II)-oxidizing microorganisms, i.e., microaerophilic, anoxygenic phototrophic, and nitrate-reducing Fe(II) oxidizers. However, it is unknown whether all three groups coexist in one habitat and how they are spatially distributed in relation to gradients of O 2 , light, nitrate, and Fe(II). We examined two coastal marine sediments in Aarhus Bay, Denmark, by cultivation and most probable number ( Fe(III)-reducing microorganisms were discovered in the late 1980s (6). Many of the better-known Fe(III)-reducing bacteria of the genera Shewanella, Geobacter, and Geothrix are found mainly in freshwater and more rarely in marine sediments (7,8). Still, Fe(III) reduction can account for a large fraction of organic-matter mineralization in coastal marine sediments (up to 50%) (9).Fe(II)-oxidizing bacteria were first described in 1836 by Ehrenberg (10) as so-called "iron bacteria." It took more than a century before the first microbes belonging to this group could be grown in the laboratory (11) and even longer until it was demonstrated that they grow autotrophically by oxidizing Fe(II) with O 2 (12). These bacteria face the problem that, at neutral pH, the abiotic reaction of oxygen and Fe(II) is fast. Therefore, bacterial Fe(II) oxidation with O 2 at neutral pH is limited to micro-oxic ([O 2 ] Ͻ 50 M) conditions, where microbial iron oxidation can compete favorably with the [O 2 ]-limited abiotic reaction (13,14). Favorable conditions for the growth of microaerophilic Fe(II) oxidizers are found in opposing gradients of Fe(II) and O 2 , e.g., in the oxicanoxic transition zone in sediments or groundwater seeps (15). Today, there are at least four known groups of exclusively microaerophilic Fe(II) oxidizers, i.e., Gallionella (11, 12), Sideroxydans (3), Leptothrix (16,17), and Mariprofundus (18). Furthermore, certain bacteria belonging to the genera Marinobacter and Hyphomonas are also described as growing under micro-oxic conditions by Fe(II) oxidation (19,20).The photoferrotrophs (5) are not only of interest for modern habitats, but may also be responsible for the formation of banded iron formations (BIFs) in the Precambrian (21,22). Until now, only a few pure cultures have been known, and there is no known monophylogenetic group that specializes solely in anoxygenic phototrophic Fe(II) oxidation. Known strains are metabolically flexible and belong to various physiological groups of anoxygenic phototrophs, i.e., the purple sulfur, purple nonsulfur, and green anoxygenic phototrophic bacteria (5,(23)(24)(25).For the nitrate-reducing Fe(II) oxidizers, most known strains cannot be maintained in culture over several transfers with nitrate

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“…To investigate the effect of electron shuttles on Feammox, six treatments (n = 3 each) were set 24 Briefly, for Fe(II) determination, 100 μL of culture suspension was transferred anaerobically with a syringe into 900 μL of 40 mmol L −1 sulfamic acid for 1 h of incubation at room temperature. Total Fe was extracted with 20 mmol L −1 hydroxylamine hydrochloride in 20 mmol L −1 sulfamic acid.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Electron Shuttles Enhance Anaerobic Ammonium Oxidation Coupled to Iron(III) Reduction

Zhou

Yang

et al. 2016

Environ. Sci. Technol.

247

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Anaerobic ammonium oxidation coupled to iron(III) reduction, termed Feammox, is a newly discovered nitrogen cycling process. However, little is known about the roles of electron shuttles in the Feammox reactions. In this study, two forms of Fe(III) (oxyhydr)oxide ferrihydrite (ex situ ferrihydrite and in situ ferrihydrite) were used in dissimilatory Fe(III) reduction (DIR) enrichments from paddy soil. Evidence for Feammox in DIR enrichments was demonstrated using the 15N-isotope tracing technique. The extent and rate of both the 30N2–29N2 and Fe(II) formation were enhanced when amended with electron shuttles (either 9,10-anthraquinone-2,6-disulfonate (AQDS) or biochar) and further simulated when these two shuttling compounds were combined. Although the Feammox-associated Fe(III) reduction accounted for only a minor proportion of total Fe(II) formation compared to DIR, it was estimated that the potentially Feammox-mediated N loss (0.13–0.48 mg N L–1 day–1) was increased by 17–340% in the enrichments by the addition of electron shuttles. The addition of electron shuttles led to an increase in the abundance of unclassified Pelobacteraceae, Desulfovibrio, and denitrifiers but a decrease in Geobacter. Overall, we demonstrated a stimulatory effect of electron shuttles on Feammox that led to higher N loss, suggesting that electron shuttles might play a crucial role in Feammox-mediated N loss from soils.

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Abiotic oxidation of Fe(II) by reactive nitrogen species in cultures of the nitrate‐reducing Fe(II) oxidizer Acidovorax sp. BoFeN1 – questioning the existence of enzymatic Fe(II) oxidation

Cited by 230 publications

References 64 publications

Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

Coexistence of Microaerophilic, Nitrate-Reducing, and Phototrophic Fe(II) Oxidizers and Fe(III) Reducers in Coastal Marine Sediment

Electron Shuttles Enhance Anaerobic Ammonium Oxidation Coupled to Iron(III) Reduction

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