Reduction of nitrate to ammonium by sulphate green rust: activation energy and reaction mechanism

Hansen, Holger Bernt; Koch, Christian

doi:10.1180/000985598545453

Cited by 123 publications

(82 citation statements)

References 25 publications

(28 reference statements)

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“…In addition, these studies also demonstrated that the oxidized iron end product formed [amorphous Fe(III) (hydr)oxide or carbonate-containing green rusts] was dependent on the rate of Fe(II) oxidation by this organism (15,38). Both of these forms of iron are known to be unstable in the environment and are strong adsorbents for HMR (4,5,25,30,31).…”

Section: Resultsmentioning

confidence: 77%

Immobilization of Radionuclides and Heavy Metals through Anaerobic Bio-Oxidation of Fe(II)

Lack

Chaudhuri

Kelly

et al. 2002

Appl Environ Microbiol

109

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Adsorption of heavy metals and radionuclides (HMR) onto iron and manganese oxides has long been recognized as an important reaction for the immobilization of these compounds. However, in environments containing elevated concentrations of these HMR the adsorptive capacity of the iron and manganese oxides may well be exceeded, and the HMR can migrate as soluble compounds in aqueous systems. Here we demonstrate the potential of a bioremediative strategy for HMR stabilization in reducing environments based on the recently described anaerobic nitrate-dependent Fe(II) oxidation by Dechlorosoma species. Bio-oxidation of 10 mM Fe(II) and precipitation of Fe(III) oxides by these organisms resulted in rapid adsorption and removal of 55 M uranium and 81 M cobalt from solution. The adsorptive capacity of the biogenic Fe(III) oxides was lower than that of abiotically produced Fe(III) oxides (100 M for both metals), which may have been a result of steric hindrance by the microbial cells on the iron oxide surfaces. The binding capacity of the biogenic oxides for different heavy metals was indirectly correlated to the atomic radius of the bound element. X-ray absorption spectroscopy indicated that the uranium was bound to the biogenically produced Fe(III) oxides as U(VI) and that the U(VI) formed bidentate and tridentate inner-sphere complexes with the Fe(III) oxide surfaces. Dechlorosoma suillum oxidation was specific for Fe(II), and the organism did not enzymatically oxidize U(IV) or Co(II). Small amounts (less than 2.5 M) of Cr(III) were reoxidized by D. suillum; however, this appeared to be inversely dependent on the initial concentration of the Cr(III). The results of this study demonstrate the potential of this novel approach for stabilization and immobilization of HMR in the environment.

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Section: Resultsmentioning

confidence: 77%

Immobilization of Radionuclides and Heavy Metals through Anaerobic Bio-Oxidation of Fe(II)

Lack

Chaudhuri

Kelly

et al. 2002

Appl Environ Microbiol

109

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“…Meanwhile, the methanol resulting from methane oxidation on green rust-like di-iron centres comprising the outer zone of the inorganic membrane will be further oxidized to formaldehyde at a Mo centre resembling that performing nitrite reduction [110,111]. The reducing power of the electrons issuing from this reaction is sufficient (cf.…”

Section: A Bioinspired Scenario For the Earliest Energy And Carbon Mementioning

confidence: 99%

Beating the acetyl coenzyme A-pathway to the origin of life

Nitschke

Russell

2013

Phil. Trans. R. Soc. B

115

174

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Attempts to draft plausible scenarios for the origin of life have in the past mainly built upon palaeogeochemical boundary conditions while, as detailed in a companion article in this issue, frequently neglecting to comply with fundamental thermodynamic laws. Even if demands from both palaeogeochemistry and thermodynamics are respected, then a plethora of strongly differing models are still conceivable. Although we have no guarantee that life at its origin necessarily resembled biology in extant organisms, we consider that the only empirical way to deduce how life may have emerged is by taking the stance of assuming continuity of biology from its inception to the present day. Building upon this conviction, we have assessed extant types of energy and carbon metabolism for their appropriateness to conditions probably pertaining in those settings of the Hadean planet that fulfil the thermodynamic requirements for life to come into being. Wood–Ljungdahl (WL) pathways leading to acetyl CoA formation are excellent candidates for such primordial metabolism. Based on a review of our present understanding of the biochemistry and biophysics of acetogenic, methanogenic and methanotrophic pathways and on a phylogenetic analysis of involved enzymes, we propose that a variant of modern methanotrophy is more likely than traditional WL systems to date back to the origin of life. The proposed model furthermore better fits basic thermodynamic demands and palaeogeochemical conditions suggested by recent results from extant alkaline hydrothermal seeps.

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“…On prolonged incubation (14 days), the green rusts gradually transformed into blackish brown-green. Previous studies have demonstrated that green rust will chemically react with nitrate to form magnetite and ammonia as the sole end products (18,19). Since green rust is one of the precursors of magnetite formed by D. suillum with nitrate as the electron acceptor, it is possible that the biogenic green rusts are abiotically reacting with the remaining nitrate to form magnetite.…”

mentioning

confidence: 99%