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Martocello DE, Wankel SD. Physiological Influence of Fe and Cu Availability on Nitrogen Isotope Fractionation during Ammonia Oxidation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:421-431. [PMID: 38147309 DOI: 10.1021/acs.est.3c05964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Microbially mediated cycling processes play central roles in regulating the speciation and availability of nitrogen, a vital nutrient with wide implications for agriculture, water quality, wastewater treatment, ecosystem health, and climate change. Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by bacteria (AOB) and archaea (AOA) that require the trace metal micronutrients copper (Cu) and iron (Fe) for growth and metabolic catalysis. While stable isotope analyses for constraining nitrogen cycling are commonly used, it is unclear whether metal availability may modulate expression of stable isotope fractionation during ammonia oxidation, by varying growth or through regulation of metabolic metalloenzymes. We present the first study examining the influence of Fe and Cu availability on the kinetic nitrogen isotope effect in ammonia oxidation (15εAO). We report a general independence of 15εAO from the growth rate in AOB, except at a low temperature (10 °C). With AOA Nitrosopumilus maritimus SCM1, however, 15εAO decreases nonlinearly at lower oxidation rates. We examine assumptions involved in the interpretation of 15εAO values and suggest these dynamics may arise from physiological constraints that push the system toward isotopic equilibrium. These results suggest important links between isotope fractionation and environmental constraints on physiology in these key N cycling microorganisms.
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Affiliation(s)
- Donald E Martocello
- Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
- Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
| | - Scott D Wankel
- Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
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2
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Sheng Y, Baars O, Guo D, Whitham J, Srivastava S, Dong H. Mineral-Bound Trace Metals as Cofactors for Anaerobic Biological Nitrogen Fixation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:7206-7216. [PMID: 37116091 DOI: 10.1021/acs.est.3c01371] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Nitrogenase is the only known biological enzyme capable of reducing N2 to bioavailable NH3. Most nitrogenases use Mo as a metallocofactor, while alternative cofactors V and Fe are also viable. Both geological and bioinformatic evidence suggest an ancient origin of Mo-based nitrogenase in the Archean, despite the low concentration of dissolved Mo in the Archean oceans. This apparent paradox would be resolvable if mineral-bound Mo were bioavailable for nitrogen fixation by ancient diazotrophs. In this study, the bioavailability of mineral-bound Mo, V, and Fe was determined by incubating an obligately anaerobic diazotroph Clostridium kluyveri with Mo-, V-, and Fe-bearing minerals (molybdenite, cavansite, and ferrihydrite, respectively) and basalt under diazotrophic conditions. The results showed that C. kluyveri utilized mineral-associated metals to express nitrogenase genes and fix nitrogen, as measured by the reverse transcription quantitative polymerase chain reaction and acetylene reduction assay, respectively. C. kluyveri secreted chelating molecules to extract metals from the minerals. As a result of microbial weathering, mineral surface chemistry significantly changed, likely due to surface coating by microbial exudates for metal extraction. These results provide important support for the ancient origin of Mo-based nitrogenase, with profound implications for coevolution of the biosphere and geosphere.
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Affiliation(s)
- Yizhi Sheng
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Oliver Baars
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Dongyi Guo
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
| | - Jason Whitham
- Department of Plant and Molecular Biology, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Shreya Srivastava
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
| | - Hailiang Dong
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
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3
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Zhu K, Hopwood MJ, Groenenberg JE, Engel A, Achterberg EP, Gledhill M. Influence of pH and Dissolved Organic Matter on Iron Speciation and Apparent Iron Solubility in the Peruvian Shelf and Slope Region. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:9372-9383. [PMID: 34110803 DOI: 10.1021/acs.est.1c02477] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The chemical speciation of iron (Fe) in oceans is influenced by ambient pH, dissolved oxygen, and the concentrations and strengths of the binding sites of dissolved organic matter (DOM). Here, we derived new nonideal competitive adsorption (NICA) constants for Fe(III) binding to marine DOM via pH-Fe titrations. We used the constants to calculate Fe(III) speciation and derive the apparent Fe(III) solubility (SFe(III)app) in the ambient water column across the Peruvian shelf and slope region. We define SFe(III)app as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). A ca. twofold increase in SFe(III)app in the oxygen minimum zone (OMZ) compared to surface waters is predicted. The increase results from a one order of magnitude decrease in H+ concentration which impacts both Fe(III) hydroxide solubility and organic complexation. A correlation matrix suggests that changes in pH have a larger impact on SFe(III)app and Fe(III) speciation than DOM in this region. Using Fe(II) measurements, we calculated ambient DFe(III) and compared the value with the predicted SFe(III)app. The underlying distribution of ambient DFe(III) largely reflected the predicted SFe(III)app, indicating that decreased pH as a result of OMZ intensification and ocean acidification may increase SFe(III)app with potential impacts on surface DFe inventories.
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Affiliation(s)
- Kechen Zhu
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany
| | - Mark J Hopwood
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany
| | - Jan E Groenenberg
- Department of Environmental Sciences, Wageningen University, P.O. Box 47, Wageningen 6700 AA, The Netherlands
| | - Anja Engel
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany
| | - Eric P Achterberg
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany
| | - Martha Gledhill
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, Kiel 24148, Germany
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4
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Butler A, Harder T, Ostrowski AD, Carrano CJ. Photoactive siderophores: Structure, function and biology. J Inorg Biochem 2021; 221:111457. [PMID: 34010741 DOI: 10.1016/j.jinorgbio.2021.111457] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/30/2021] [Accepted: 04/03/2021] [Indexed: 12/17/2022]
Abstract
It is well known that bacteria and fungi have evolved sophisticated systems for acquiring the abundant but biologically inaccessible trace element iron. These systems are based on high affinity Fe(III)-specific binding compounds called siderophores which function to acquire, transport, and process this essential metal ion. Many hundreds of siderophores are now known and their numbers continue to grow. Extensive studies of their isolation, structure, transport, and molecular genetics have been undertaken in the last three decades and have been comprehensively reviewed many times. In this review we focus on a unique subset of siderophores that has only been recognized in the last 20 years, namely those whose iron complexes display photoactivity. This photoactivity, which typically results in the photooxidation of the siderophore ligand with concomitant reduction of Fe(III) to Fe(II), seemingly upsets the siderophore paradigm of forming and transporting only extremely stable Fe(III) complexes into microbial cells. Here we review their structure, synthesis, photochemistry, photoproduct coordination chemistry and explore the potential biological and ecological consequences of this photoactivity.
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Affiliation(s)
- Alison Butler
- Department of Chemistry and Biochemistry University of California, Santa Barbara, CA 93106 United States
| | - Tilmann Harder
- Department of Biology and Chemistry, University of Bremen, and Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Germany
| | | | - Carl J Carrano
- Department of Chemistry and Biochemistry, San Diego State University, United States.
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5
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Tanaka K, Shimakawa G, Kusama S, Harada T, Kato S, Nakanishi S. Ferrihydrite Reduction by Photosynthetic Synechocystis sp. PCC 6803 and Its Correlation With Electricity Generation. Front Microbiol 2021; 12:650832. [PMID: 33763051 PMCID: PMC7982531 DOI: 10.3389/fmicb.2021.650832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/16/2021] [Indexed: 11/29/2022] Open
Abstract
Microbial extracellular electron transfer (EET) to solid-state electron acceptors such as anodes and metal oxides, which was originally identified in dissimilatory metal-reducing bacteria, is a key process in microbial electricity generation and the biogeochemical cycling of metals. Although it is now known that photosynthetic microorganisms can also generate (photo)currents via EET, which has attracted much interest in the field of biophotovoltaics, little is known about the reduction of metal (hydr)oxides via photosynthetic microbial EET. The present work quantitatively assessed the reduction of ferrihydrite in conjunction with the EET of the photosynthetic microbe Synechocystis sp. PCC 6803. Microbial reduction of ferrihydrite was found to be initiated in response to light but proceeded at higher rates when exogenous glucose was added, even under dark conditions. These results indicate that current generation from Synechocystis cells does not always need light irradiation. The qualitative trends exhibited by the ferrihydrite reduction rates under various conditions showed significant correlation with those of the microbial currents. Notably, the maximum concentration of Fe(II) generated by the cyanobacterial cells under dark conditions in the presence of glucose was comparable to the levels observed in the photic layers of Fe-rich microbial mats.
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Affiliation(s)
- Kenya Tanaka
- Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
| | - Ginga Shimakawa
- Research Center for Solar Energy Chemistry, Osaka University, Toyonaka, Japan
| | - Shoko Kusama
- Research Center for Solar Energy Chemistry, Osaka University, Toyonaka, Japan
| | - Takashi Harada
- Research Center for Solar Energy Chemistry, Osaka University, Toyonaka, Japan
| | - Souichiro Kato
- Research Center for Solar Energy Chemistry, Osaka University, Toyonaka, Japan.,Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Sapporo, Japan
| | - Shuji Nakanishi
- Graduate School of Engineering Science, Osaka University, Toyonaka, Japan.,Research Center for Solar Energy Chemistry, Osaka University, Toyonaka, Japan
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6
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Luo Z, Min Y, Qu L, Song Y, Hong Y. Remediation of phenanthrene contaminated soil by ferrous oxalate and its phytotoxicity evaluation. CHEMOSPHERE 2021; 265:129070. [PMID: 33257048 DOI: 10.1016/j.chemosphere.2020.129070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 10/17/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Phenanthrene contaminated soil was remediated by the photochemical process of ferrous oxalate. Without using H2O2 and adjusting soil pH, phenanthrene in contaminated soil was degraded effectively by the ferrous oxalate under visible light irradiation. Ferrous oxalate possesses excellent visible light absorption ability which benefits the degradation of phenanthrene in soil under visible light irradiation. Via the Fe(II)/Fe(III) catalytic cycle of ferrous oxalate, H2O2 and Fe(II) could be produced continuously and H2O2 was further catalyzed by Fe(II) and released hydroxyl radicals (•OH) to degrade the phenanthrene in soil. The dosage of ferrous oxalate, moisture content of soil, and soil thickness were most important factors for degradation of phenanthrene in soil. In addition, a good mixing of ferrous oxalate and soil was vital for enhancing the degradation ratio of phenanthrene. After phenanthrene contaminated soil was treated by ferrous oxalate, the toxicity of treated soil was evaluated via the lettuce cultivation experiments. It was demonstrated the toxicity of phenanthrene contaminated soil was significantly reduced by ferrous oxalate according to the growth indexes of lettuces, including root length, leaf length, and fresh weight. This environment-friendly soil remediation method based on ferrous oxalate has huge potential in the remediation of organic pollutant contaminated soil.
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Affiliation(s)
- Zhijun Luo
- School of the Environment and Safety Engineering, Jiangsu University, 301 Xuefu Road Zhenjiang, 212013, China; Yangzhou Tiancheng Water Treatment Equipment Engineering Co., LTD, Yangzhou, 225000, China.
| | - Yanghong Min
- School of the Environment and Safety Engineering, Jiangsu University, 301 Xuefu Road Zhenjiang, 212013, China
| | - Lingling Qu
- School of Chemistry and Chemical Engineering, Jiangsu University, 301 Xuefu Road Zhenjiang, 212013, China.
| | - Youye Song
- School of the Environment and Safety Engineering, Jiangsu University, 301 Xuefu Road Zhenjiang, 212013, China
| | - Yongxiang Hong
- School of the Environment and Safety Engineering, Jiangsu University, 301 Xuefu Road Zhenjiang, 212013, China
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7
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Shafiee RT, Snow JT, Zhang Q, Rickaby REM. Iron requirements and uptake strategies of the globally abundant marine ammonia-oxidising archaeon, Nitrosopumilus maritimus SCM1. THE ISME JOURNAL 2019; 13:2295-2305. [PMID: 31076641 PMCID: PMC6776035 DOI: 10.1038/s41396-019-0434-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 04/04/2019] [Accepted: 04/15/2019] [Indexed: 01/08/2023]
Abstract
Ammonia-oxidising archaea (AOA) mediate the rate-limiting step of nitrification, the central component of the marine nitrogen cycle that converts ammonia to nitrite then nitrate. Competition with phytoplankton for ammonium and light inhibition are considered to restrict AOA activity to below the photic zone, but observations of surface nitrification now demand a further understanding of the factors driving AOA distribution and activity. Pico- to nanomolar concentrations of iron (Fe) limit the growth of microorganisms in a significant portion of the world's surface oceans, yet there is no examination of the role of Fe in AOA growth despite the process of ammonia oxidation being considered to rely on the micronutrient. Here we investigate the Fe requirements and Fe uptake strategies of the Nitrosopumilus maritimus strain SCM1, a strain representative of globally abundant marine AOA. Using trace metal clean culturing techniques, we found that N. maritimus growth is determined by Fe availability, displaying a free inorganic Fe (Fe') half saturation constant 1-2 orders of magnitude greater for cell growth than numerous marine phytoplankton and heterotrophic bacterial species driven by a reduced affinity for Fe'. In addition, we discovered that whilst unable to produce siderophores to enhance access to Fe, N. maritimus is able to use the exogenous siderophore desferrioxamine B (DFB), likely through a reductive uptake pathway analogous to that demonstrated in phytoplankton. Our work suggests AOA growth in surface waters may be Fe limited and advances our understanding of AOA physiology on the cellular and mechanistic levels with implications for ecosystem dynamics and the biogeochemical N-cycle.
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Affiliation(s)
- Roxana T Shafiee
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxfordshire, OX1 3AN, UK.
| | - Joseph T Snow
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxfordshire, OX1 3AN, UK
| | - Qiong Zhang
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxfordshire, OX1 3AN, UK
| | - Rosalind E M Rickaby
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxfordshire, OX1 3AN, UK
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8
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Lin P, Xu C, Kaplan DI, Chen H, Yeager CM, Xing W, Sun L, Schwehr KA, Yamazaki H, Saito-Kokubu Y, Hatcher PG, Santschi PH. Nagasaki sediments reveal that long-term fate of plutonium is controlled by select organic matter moieties. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 678:409-418. [PMID: 31077919 DOI: 10.1016/j.scitotenv.2019.04.375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 06/09/2023]
Abstract
Forecasting the long-term fate of plutonium (Pu) is becoming increasingly important as more worldwide military and nuclear-power waste is being generated. Nagasaki sediments containing bomb-derived Pu that was deposited in 1945 provided a unique opportunity to explore the long-term geochemical behavior of Pu. Through a combination of selective extractions and molecular characterization via electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS), we determined that 55 ± 3% of the bomb-derived 239,240Pu was preferentially associated with more persistent organic matter compounds in Nagasaki sediments, particularly those natural organic matter (NOM) stabilized by Fe oxides (NOMFe-oxide). Other organic matter compounds served as a secondary sink of these bomb-derived 239,240Pu (31 ± 2% on average), and <20% of the 239,240Pu was immobilized by inorganic mineral particles. In a narrow, 239,240Pu-enriched layer of only 9-cm depth (total core depth was 600 cm), N-containing carboxyl aliphatic and/or alicyclic molecules (CCAM) in NOMFe-oxide and other NOM fractions immobilized the majority of 239,240Pu. Among the cluster of N-containing CCAM moieties, hydroxamate siderophores, the strongest known Pu chelators in nature, were further detected in these "aged" Nagasaki bomb residue-containing sediments. While present long-term disposal and environmental remediation modeling assume that solubility limits and sorption to mineral surfaces control Pu subsurface mobility, our observations suggest that NOM, which is present in essentially all subsurface systems, undoubtedly plays an important role in sequestrering Pu. Ignoring the role of NOM in controlling Pu fate and transport is not justified in most environmental systems.
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Affiliation(s)
- Peng Lin
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States.
| | - Chen Xu
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States
| | - Daniel I Kaplan
- Savannah River National Laboratory, Aiken, SC 29808, United States
| | - Hongmei Chen
- Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University, Norfolk, VA 23529, United States
| | - Chris M Yeager
- Los Alamos National Laboratory, Los Alamos, NM 87545, United States
| | - Wei Xing
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States
| | - Luni Sun
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States
| | - Kathleen A Schwehr
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States
| | - Hideo Yamazaki
- Formally from Kindai University, Higashi-osaka, Osaka Prefecture 577-8502, Japan
| | - Yoko Saito-Kokubu
- Tono Geoscience Center, Japan Atomic Energy Agency, Jorinji, Izumicho, Toki-Shi, Gifu Prefecture 509-5102, Japan
| | - Patrick G Hatcher
- Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University, Norfolk, VA 23529, United States
| | - Peter H Santschi
- Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States
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9
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Peng C, Bryce C, Sundman A, Kappler A. Cryptic Cycling of Complexes Containing Fe(III) and Organic Matter by Phototrophic Fe(II)-Oxidizing Bacteria. Appl Environ Microbiol 2019; 85:e02826-18. [PMID: 30796062 PMCID: PMC6450027 DOI: 10.1128/aem.02826-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 02/14/2019] [Indexed: 11/20/2022] Open
Abstract
Fe-organic matter (Fe-OM) complexes are abundant in the environment and, due to their mobility, reactivity, and bioavailability, play a significant role in the biogeochemical Fe cycle. In photic zones of aquatic environments, Fe-OM complexes can potentially be reduced and oxidized, and thus cycled, by light-dependent processes, including abiotic photoreduction of Fe(III)-OM complexes and microbial oxidation of Fe(II)-OM complexes, by anoxygenic phototrophic bacteria. This could lead to a cryptic iron cycle in which continuous oxidation and rereduction of Fe could result in a low and steady-state Fe(II) concentration despite rapid Fe turnover. However, the coupling of these processes has never been demonstrated experimentally. In this study, we grew a model anoxygenic phototrophic Fe(II) oxidizer, Rhodobacter ferrooxidans SW2, with either citrate, Fe(II)-citrate, or Fe(III)-citrate. We found that strain SW2 was capable of reoxidizing Fe(II)-citrate produced by photochemical reduction of Fe(III)-citrate, which kept the dissolved Fe(II)-citrate concentration at low (<10 μM) and stable concentrations, with a concomitant increase in cell numbers. Cell suspension incubations with strain SW2 showed that it can also oxidize Fe(II)-EDTA, Fe(II)-humic acid, and Fe(II)-fulvic acid complexes. This work demonstrates the potential for active cryptic Fe cycling in the photic zone of anoxic aquatic environments, despite low measurable Fe(II) concentrations which are controlled by the rate of microbial Fe(II) oxidation and the identity of the Fe-OM complexes.IMPORTANCE Iron cycling, including reduction of Fe(III) and oxidation of Fe(II), involves the formation, transformation, and dissolution of minerals and dissolved iron-organic matter compounds. It has been shown previously that Fe can be cycled so rapidly that no measurable changes in Fe(II) and Fe(III) concentrations occur, leading to a so-called cryptic cycle. Cryptic Fe cycles have been shown to be driven either abiotically by a combination of photochemical reduction of Fe(III)-OM complexes and reoxidation of Fe(II) by O2, or microbially by a combination of Fe(III)-reducing and Fe(II)-oxidizing bacteria. Our study demonstrates a new type of light-driven cryptic Fe cycle that is relevant for the photic zone of aquatic habitats involving abiotic photochemical reduction of Fe(III)-OM complexes and microbial phototrophic Fe(II) oxidation. This new type of cryptic Fe cycle has important implications for biogeochemical cycling of iron, carbon, nutrients, and heavy metals and can also influence the composition and activity of microbial communities.
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Affiliation(s)
- Chao Peng
- Geomicrobiology Center for Applied Geoscience, University of Tübingen, Tübingen, Germany
| | - Casey Bryce
- Geomicrobiology Center for Applied Geoscience, University of Tübingen, Tübingen, Germany
| | - Anneli Sundman
- Geomicrobiology Center for Applied Geoscience, University of Tübingen, Tübingen, Germany
| | - Andreas Kappler
- Geomicrobiology Center for Applied Geoscience, University of Tübingen, Tübingen, Germany
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10
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Barazesh J, Prasse C, Wenk J, Berg S, Remucal CK, Sedlak DL. Trace Element Removal in Distributed Drinking Water Treatment Systems by Cathodic H 2O 2 Production and UV Photolysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:195-204. [PMID: 29240414 PMCID: PMC5772888 DOI: 10.1021/acs.est.7b04396] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
As water scarcity intensifies, point-of-use and point-of-entry treatment may provide a means of exploiting locally available water resources that are currently considered to be unsafe for human consumption. Among the different classes of drinking water contaminants, toxic trace elements (e.g., arsenic and lead) pose substantial operational challenges for distributed drinking water treatment systems. Removal of toxic trace elements via adsorption onto iron oxides is an inexpensive and robust treatment method; however, the presence of metal-complexing ligands associated with natural organic matter (NOM) often prevents the formation of iron precipitates at the relatively low concentrations of dissolved iron typically present in natural water sources, thereby requiring the addition of iron which complicates the treatment process and results in a need to dispose of relatively large amounts of accumulated solids. A point-of-use treatment device consisting of a cathodic cell that produced hydrogen peroxide (H2O2) followed by an ultraviolet (UV) irradiation chamber was used to decrease colloid stabilization and metal-complexing capacity of NOM present in groundwater. Exposure to UV light altered NOM, converting ∼6 μM of iron oxides into settable forms that removed between 0.5 and 1 μM of arsenic (As), lead (Pb), and copper (Cu) from solution via adsorption. After treatment, changes in NOM consistent with the loss of iron-complexing carboxylate ligands were observed, including decreases in UV absorbance and shifts in the molecular composition of NOM to higher H/C and lower O/C ratios. Chronoamperometric experiments conducted in synthetic groundwater revealed that the presence of Ca2+ and Mg2+ inhibited intramolecular charge-transfer within photoexcited NOM, leading to substantially increased removal of iron and trace elements.
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Affiliation(s)
- James
M. Barazesh
- Department
of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720 United States
- Carollo
Engineers, Inc., Costa Mesa, California 92626, United States
| | - Carsten Prasse
- Department
of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720 United States
| | - Jannis Wenk
- Department
of Chemical Engineering and Water Innovation & Research Centre, University of Bath, Claverton Down, Bath, BA2 7AY United Kingdom
| | - Stephanie Berg
- Environmental
Chemistry & Technology Program, University
of Wisconsin-Madison, Madison, Wisconsin 53706 United States
| | - Christina K. Remucal
- Environmental
Chemistry & Technology Program, University
of Wisconsin-Madison, Madison, Wisconsin 53706 United States
- Department
of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 United States
| | - David L. Sedlak
- Department
of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720 United States
- E-mail:
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11
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Lee YP, Fujii M, Kikuchi T, Terao K, Yoshimura C. Variation of iron redox kinetics and its relation with molecular composition of standard humic substances at circumneutral pH. PLoS One 2017; 12:e0176484. [PMID: 28453538 PMCID: PMC5409151 DOI: 10.1371/journal.pone.0176484] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/11/2017] [Indexed: 11/18/2022] Open
Abstract
Oxidation and reduction kinetics of iron (Fe) and proportion of steady-state Fe(II) concentration relative to total dissolved Fe (steady-state Fe(II) fraction) were investigated in the presence of various types of standard humic substances (HS) with particular emphasis on the photochemical and thermal reduction of Fe(III) and oxidation of Fe(II) by dissolved oxygen (O2) and hydrogen peroxide (H2O2) at circumneutral pH (pH 7–8). Rates of Fe(III) reduction were spectrophotometrically determined by a ferrozine method under the simulated sunlight and dark conditions, whereas rates of Fe(II) oxidation were examined in air-saturated solution using luminol chemiluminescence technique. The reduction and oxidation rate constants were determined to substantially vary depending on the type of HS. For example, the first-order rate constants varied by up to 10-fold for photochemical reduction and 7-fold for thermal reduction. The degree of variation in Fe(II) oxidation was larger for the H2O2-mediated reaction compared to the O2-mediated reaction (e.g., 15- and 3-fold changes for the former and latter reactions, respectively, at pH 8). The steady-state Fe(II) fraction under the simulated sunlight indicated that the Fe(II) fraction varies by up to 12-fold. The correlation analysis indicated that variation of Fe(II) oxidation is significantly associated with aliphatic content of HS, suggesting that Fe(II) complexation by aliphatic components accelerates Fe(II) oxidation. The reduction rate constant and steady-state Fe(II) fractions in the presence of sunlight had relatively strong positive relations with free radical content of HS, possibly due to the reductive property of radical semiquinone in HS. Overall, the findings in this study indicated that the Fe reduction and oxidation kinetics and resultant Fe(II) formation are substantially influenced by chemical properties of HS.
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Affiliation(s)
- Ying Ping Lee
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Manabu Fujii
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- * E-mail:
| | - Tetsuro Kikuchi
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- Ibaraki Kasumigaura Environmental Science Center, Okijyuku-machi, Tsuchiura, Ibaraki, Japan
| | - Koumei Terao
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Chihiro Yoshimura
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
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12
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Liu R, Zhu X, Chen B. A New Insight of Graphene oxide-Fe(III) Complex Photochemical Behaviors under Visible Light Irradiation. Sci Rep 2017; 7:40711. [PMID: 28084446 PMCID: PMC5234028 DOI: 10.1038/srep40711] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 12/09/2016] [Indexed: 11/09/2022] Open
Abstract
Graphene oxide (GO) contains not only aromatic carbon lattice but also carboxyl groups which enhanced the aqueous solubility of GO. To study the transformation of GO nanosheets in natural environments, GO aqueous dispersion was mixed with Fe3+ ions to form photoactive complex. Under visible light irradiation, Fe(III) of the complex would be reduced to Fe(II) which could subsequently reduce highly toxic Cr(VI) to Cr3+. The electron of the reduction was contributed by the decarboxylation of carboxyl groups on GO and iron was acting as a catalyst during the photoreduction. On the other hand, the consumption of carboxyl groups may convert GO to rGO which are tend to aggregate since the decreased electrostatic repulsion and the increased π-π attraction. The formed Cr3+ may be electrostatically adsorbed by the rGO sheets and simultaneously precipitated with the aggregated rGO sheets, resulting the effective removal of chromium and GO nanosheets from the aqueous environment. This study may shed a light on understanding the environmental transformation of GO and guide the treatment of Cr(VI).
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Affiliation(s)
- Renlan Liu
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
| | - Xiaoying Zhu
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
| | - Baoliang Chen
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
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13
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Wang Y, Zhang P. Enhanced photochemical decomposition of environmentally persistent perfluorooctanoate by coexisting ferric ion and oxalate. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:9660-9668. [PMID: 26846242 DOI: 10.1007/s11356-016-6205-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 01/29/2016] [Indexed: 06/05/2023]
Abstract
Perfluorooctanoic acid (PFOA), an environmentally persistent pollutant, was found to be quickly decomposed under 254 nm UV irradiation in the presence of ferric ion and oxalic acid. To understand the PFOA decomposition mechanism by this process, the effects of reaction atmosphere and concentrations of ferric ions and oxalic acids on PFOA decomposition were investigated, as well as decomposition intermediates. PFOA mainly decomposes via two pathways: (i) photochemical oxidation via Fe(III)-PFOA complexes and (ii) one-electron reduction caused by carboxylate anion radical (CO2 (•-)), which was generated by photolysis of ferrioxalate complexes. Under excess oxalic acid, PFOA decomposition was accelerated, and its corresponding half-life was shortened from 114 to 34 min as ferric concentration increased from 7 to 80 μM. Besides fluoride ions, six shorter chain perfluorinated carboxylic acids (PFCAs) bearing C2-C7 were identified as main intermediates. The presence of O2 promoted the redox recycling of Fe(3+)/Fe(2+) and thus avoided the exhaustion of the Fe(III).
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Affiliation(s)
- Yuan Wang
- College of Resource and Environmental Engineering, Guizhou University, Guiyang, Guizhou Province, 550025, People's Republic of China
| | - Pengyi Zhang
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, People's Republic of China.
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14
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Fujii M, Yeung ACY, Waite TD. Competitive Effects of Calcium and Magnesium Ions on the Photochemical Transformation and Associated Cellular Uptake of Iron by the Freshwater Cyanobacterial Phytoplankton Microcystis aeruginosa. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:9133-42. [PMID: 26132788 DOI: 10.1021/acs.est.5b01583] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Photochemical reduction of iron and iron uptake by Microcystis were investigated in a freshwater medium (pH 8) containing a range of calcium (Ca) and magnesium (Mg) ion concentrations (0.002-20 mM). In a medium containing the chelator ethylenediaminetetraacetic acid (EDTA), 50-fold increases in net photochemical formation rates of unchelated ferrous iron (Fe(II)') were observed as the concentration of calcium or magnesium metal (Me) was increased to exceed the concentration of EDTA. Kinetic modeling of iron transformation processes indicated that the facilitated Fe(II)' formation is attributed to Me-promoted photoreductive dissociation of the ferric iron-EDTA complex. In the medium containing Suwanee River fulvic acid, in contrast, the competitive effect of Me on photochemical Fe(II)' formation appears to be negligible due to the weak binding affinities of fulvic acid to Me. The cellular iron uptake rate in the EDTA-buffered system increased by ∼3-fold in the excess Me condition where the increased rate of photochemical Fe(II)' formation was observed, whereas the presence of Me resulted in a decrease in iron uptake rate in the fulvic acid system (by up to 5-fold). The decrease in iron uptake is likely caused by Me binding to iron transporters and other entities involved in intracellular iron transport. The findings of this study indicate a significant effect of Ca and Mg concentrations in natural waters on iron uptake by Microcystis, with the magnitude of effect depending strongly on ligand type.
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Affiliation(s)
- Manabu Fujii
- †Department of Civil Engineering, Tokyo Institute of Technology, 2-12-1-M1-4 Ookayama, Tokyo 152-8552, Japan
| | - Anna C Y Yeung
- ‡School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
| | - T David Waite
- ‡School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
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15
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A Comparative Study of Iron Uptake Rates and Mechanisms amongst Marine and Fresh Water Cyanobacteria: Prevalence of Reductive Iron Uptake. Life (Basel) 2015; 5:841-60. [PMID: 25768677 PMCID: PMC4390881 DOI: 10.3390/life5010841] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 01/26/2015] [Accepted: 02/28/2015] [Indexed: 01/02/2023] Open
Abstract
In this contribution, we address the question of iron bioavailability to cyanobacteria by measuring Fe uptake rates and probing for a reductive uptake pathway in diverse cyanobacterial species. We examined three Fe-substrates: dissolved inorganic iron (Fe') and the Fe-siderophores Ferrioxamine B (FOB) and FeAerobactin (FeAB). In order to compare across substrates and strains, we extracted uptake rate constants (kin = uptake rate/[Fe-substrate]). Fe' was the most bioavailable Fe form to cyanobacteria, with kin values higher than those of other substrates. When accounting for surface area (SA), all strains acquired Fe' at similar rates, as their kin/SA were similar. We also observed homogeneity in the uptake of FOB among strains, but with 10,000 times lower kin/SA values than Fe'. Uniformity in kin/SA suggests similarity in the mechanism of uptake and indeed, all strains were found to employ a reductive step in the uptake of Fe' and FOB. In contrast, different uptake pathways were found for FeAB along with variations in kin/SA. Our data supports the existence of a common reductive Fe uptake pathway amongst cyanobacteria, functioning alone or in addition to siderophore-mediated uptake. Cyanobacteria combining both uptake strategies benefit from increased flexibility in accessing different Fe-substrates.
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16
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Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom. Proc Natl Acad Sci U S A 2015; 112:E15-20. [PMID: 25535372 DOI: 10.1073/pnas.1421576112] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The supply and bioavailability of dissolved iron sets the magnitude of surface productivity for ∼ 40% of the global ocean. The redox state, organic complexation, and phase (dissolved versus particulate) of iron are key determinants of iron bioavailability in the marine realm, although the mechanisms facilitating exchange between iron species (inorganic and organic) and phases are poorly constrained. Here we use the isotope fingerprint of dissolved and particulate iron to reveal distinct isotopic signatures for biological uptake of iron during a GEOTRACES process study focused on a temperate spring phytoplankton bloom in subtropical waters. At the onset of the bloom, dissolved iron within the mixed layer was isotopically light relative to particulate iron. The isotopically light dissolved iron pool likely results from the reduction of particulate iron via photochemical and (to a lesser extent) biologically mediated reduction processes. As the bloom develops, dissolved iron within the surface mixed layer becomes isotopically heavy, reflecting the dominance of biological processing of iron as it is removed from solution, while scavenging appears to play a minor role. As stable isotopes have shown for major elements like nitrogen, iron isotopes offer a new window into our understanding of the biogeochemical cycling of iron, thereby allowing us to disentangle a suite of concurrent biotic and abiotic transformations of this key biolimiting element.
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17
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Smith NA, Sadler PJ. Photoactivatable metal complexes: from theory to applications in biotechnology and medicine. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120519. [PMID: 23776303 PMCID: PMC3685452 DOI: 10.1098/rsta.2012.0519] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This short review highlights some of the exciting new experimental and theoretical developments in the field of photoactivatable metal complexes and their applications in biotechnology and medicine. The examples chosen are based on some of the presentations at the Royal Society Discussion Meeting in June 2012, many of which are featured in more detail in other articles in this issue. This is a young field. Even the photochemistry of well-known systems such as metal-carbonyl complexes is still being elucidated. Striking are the recent developments in theory and computation (e.g. time-dependent density functional theory) and in ultrafast-pulsed radiation techniques which allow photochemical reactions to be followed and their mechanisms to be revealed on picosecond/nanosecond time scales. Not only do some metal complexes (e.g. those of Ru and Ir) possess favourable emission properties which allow functional imaging of cells and tissues (e.g. DNA interactions), but metal complexes can also provide spatially controlled photorelease of bioactive small molecules (e.g. CO and NO)--a novel strategy for site-directed therapy. This extends to cancer therapy, where metal-based precursors offer the prospect of generating excited-state drugs with new mechanisms of action that complement and augment those of current organic photosensitizers.
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Jirsa F, Neubauer E, Kittinger R, Hofmann T, Krachler R, von der Kammer F, Keppler BK. Natural organic matter and iron export from the Tanner Moor, Austria. LIMNOLOGICA (ONLINE) 2013; 43:239-244. [PMID: 23805012 PMCID: PMC3688309 DOI: 10.1016/j.limno.2012.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 09/20/2012] [Accepted: 09/29/2012] [Indexed: 05/20/2023]
Abstract
Samples from a pristine raised peat bog runoff in Austria, the Tannermoor creek, were analysed for their iron linked to natural organic matter (NOM) content. Dissolved organic carbon < 0.45 μm (DOC) was 41-64 mg L-1, iron 4.4-5.5 mg L-1. Samples were analysed applying asymmetric field flow fractionation (AsFlFFF) coupled to UV-vis absorption, fluorescence and inductively coupled plasma mass spectrometry (ICP-MS). The samples showed an iron peak associated with the NOM peak, one sample exhibiting a second peak of iron independent from the NOM peak. As highland peat bogs with similar climatic conditions and vegetation to the Tanner Moor are found throughout the world, including areas adjacent to the sea, we examined the behaviour of NOM and iron in samples brought to euhaline (35‰) conditions with artificial sea salt. The enhanced ionic strength reduced NOM by 53% and iron by 82%. Size exclusion chromatography (SEC) of the samples at sea-like salinity revealed two major fractions of NOM associated with different iron concentrations. The larger one, eluting sharply after the upper exclusion limits of 4000-5000 g mol-1, seems to be most important for iron chelating. The results outline the global importance of sub-mountainous and mountainous raised peat bogs as a source of iron chelators to the marine environment at sites where such peat bogs release their run-offs into the sea.
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Affiliation(s)
- Franz Jirsa
- University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, 1090 Vienna, Austria
- Corresponding author. Tel.: +43 1 4277 526 27; fax: +43 1 4277 52620.
| | - Elisabeth Neubauer
- University of Vienna, Department of Environmental Geosciences, Althanstraße 14, 1090 Vienna, Austria
| | - Richard Kittinger
- University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, 1090 Vienna, Austria
| | - Thilo Hofmann
- University of Vienna, Department of Environmental Geosciences, Althanstraße 14, 1090 Vienna, Austria
| | - Regina Krachler
- University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, 1090 Vienna, Austria
| | - Frank von der Kammer
- University of Vienna, Department of Environmental Geosciences, Althanstraße 14, 1090 Vienna, Austria
| | - Bernhard K. Keppler
- University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, 1090 Vienna, Austria
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19
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Sunda WG. Feedback Interactions between Trace Metal Nutrients and Phytoplankton in the Ocean. Front Microbiol 2012; 3:204. [PMID: 22701115 PMCID: PMC3369199 DOI: 10.3389/fmicb.2012.00204] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 05/17/2012] [Indexed: 02/03/2023] Open
Abstract
In addition to control by major nutrient elements (nitrogen, phosphorus, and silicon) the productivity and species composition of marine phytoplankton communities are also regulated by a number of trace metal nutrients (iron, zinc, cobalt, manganese, copper, and cadmium). Of these, iron is most limiting to phytoplankton growth and has the greatest effect on algal species diversity. It also plays an important role in limiting di-nitrogen (N(2)) fixation rates, and thus is important in controlling ocean inventories of fixed nitrogen. Because of these effects, iron is thought to play a key role in regulating biological cycles of carbon and nitrogen in the ocean, including the biological transfer of carbon to the deep sea, the so-called biological CO(2) pump, which helps regulate atmospheric CO(2) and CO(2)-linked global warming. Other trace metal nutrients (zinc, cobalt, copper, and manganese) have lesser effects on productivity; but may exert an important influence on the species composition of algal communities because of large differences in metal requirements among species. The interactions between trace metals and ocean plankton are reciprocal: not only do the metals control the plankton, but the plankton regulate the distributions, chemical speciation, and cycling of these metals through cellular uptake and recycling processes, downward flux of biogenic particles, biological release of organic chelators, and mediation of redox reactions. This two way interaction has influenced not only the biology and chemistry of the modern ocean, but has had a profound influence on biogeochemistry of the ocean and earth system as a whole, and on the evolution of marine and terrestrial biology over geologic history.
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Affiliation(s)
- William G Sunda
- National Ocean Service, National Oceanic and Atmospheric Administration Beaufort, NC, USA
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20
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Shaked Y, Lis H. Disassembling iron availability to phytoplankton. Front Microbiol 2012; 3:123. [PMID: 22529839 PMCID: PMC3328120 DOI: 10.3389/fmicb.2012.00123] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 03/14/2012] [Indexed: 01/26/2023] Open
Abstract
The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis, and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdown in vast ocean regions. Yet a clear-cut definition of bioavailability remains elusive, with elements of iron speciation and kinetics, phytoplankton physiology, light, temperature, and microbial interactions, to name a few, all intricately intertwined into this concept. Here, in a synthesis of published and new data, we attempt to disassemble the complex concept of iron bioavailability to phytoplankton by individually exploring some of its facets. We distinguish between the fundamentals of bioavailability – the acquisition of Fe-substrate by phytoplankton – and added levels of complexity involving interactions among organisms, iron, and ecosystem processes. We first examine how phytoplankton acquire free and organically bound iron, drawing attention to the pervasiveness of the reductive uptake pathway in both prokaryotic and eukaryotic autotrophs. Turning to acquisition rates, we propose to view the availability of various Fe-substrates to phytoplankton as a spectrum rather than an absolute “all or nothing.” We then demonstrate the use of uptake rate constants to make comparisons across different studies, organisms, Fe-compounds, and environments, and for gaging the contribution of various Fe-substrates to phytoplankton growth in situ. Last, we describe the influence of aquatic microorganisms on iron chemistry and fate by way of organic complexation and bio-mediated redox transformations and examine the bioavailability of these bio-modified Fe species.
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Affiliation(s)
- Yeala Shaked
- Interuniversity Institute for Marine Sciences in Eilat Eilat, Israel
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21
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Rose AL. The influence of extracellular superoxide on iron redox chemistry and bioavailability to aquatic microorganisms. Front Microbiol 2012; 3:124. [PMID: 22514548 PMCID: PMC3323869 DOI: 10.3389/fmicb.2012.00124] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 03/15/2012] [Indexed: 11/17/2022] Open
Abstract
Superoxide, the one-electron reduced form of dioxygen, is produced in the extracellular milieu of aquatic microbes through a range of abiotic chemical processes and also by microbes themselves. Due to its ability to promote both oxidative and reductive reactions, superoxide may have a profound impact on the redox state of iron, potentially influencing iron solubility, complex speciation, and bioavailability. The interplay between iron, superoxide, and oxygen may also produce a cascade of other highly reactive transients in oxygenated natural waters. For microbes, the overall effect of reactions between superoxide and iron may be deleterious or beneficial, depending on the organism and its chemical environment. Here I critically discuss recent advances in understanding: (i) sources of extracellular superoxide in natural waters, with a particular emphasis on microbial generation; (ii) the chemistry of reactions between superoxide and iron; and (iii) the influence of these processes on iron bioavailability and microbial iron nutrition.
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Affiliation(s)
- Andrew L. Rose
- Southern Cross GeoScience, Southern Cross UniversityLismore, NSW, Australia
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22
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Affiliation(s)
- Moriah Sandy
- Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106-9510, USA
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23
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Photolysis of iron-siderophore chelates promotes bacterial-algal mutualism. Proc Natl Acad Sci U S A 2009; 106:17071-6. [PMID: 19805106 DOI: 10.1073/pnas.0905512106] [Citation(s) in RCA: 295] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Marine microalgae support world fisheries production and influence climate through various mechanisms. They are also responsible for harmful blooms that adversely impact coastal ecosystems and economies. Optimal growth and survival of many bloom-forming microalgae, including climatically important dinoflagellates and coccolithophores, requires the close association of specific bacterial species, but the reasons for these associations are unknown. Here, we report that several clades of Marinobacter ubiquitously found in close association with dinoflagellates and coccolithophores produce an unusual lower-affinity dicitrate siderophore, vibrioferrin (VF). Fe-VF chelates undergo photolysis at rates that are 10-20 times higher than siderophores produced by free-living marine bacteria, and unlike the latter, the VF photoproduct has no measurable affinity for iron. While both an algal-associated bacterium and a representative dinoflagellate partner, Scrippsiella trochoidea, used iron from Fe-VF chelates in the dark, in situ photolysis of the chelates in the presence of attenuated sunlight increased bacterial iron uptake by 70% and algal uptake by >20-fold. These results suggest that the bacteria promote algal assimilation of iron by facilitating photochemical redox cycling of this critical nutrient. Also, binary culture experiments and genomic evidence suggest that the algal cells release organic molecules that are used by the bacteria for growth. Such mutualistic sharing of iron and fixed carbon has important implications toward our understanding of the close beneficial interactions between marine bacteria and phytoplankton, and the effect of these interactions on algal blooms and climate.
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Zawadzka AM, Abergel RJ, Nichiporuk R, Andersen UN, Raymond KN. Siderophore-mediated iron acquisition systems in Bacillus cereus: Identification of receptors for anthrax virulence-associated petrobactin . Biochemistry 2009; 48:3645-57. [PMID: 19254027 DOI: 10.1021/bi8018674] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
During growth under iron limitation, Bacillus cereus and Bacillus anthracis, two human pathogens from the Bacillus cereus group of Gram-positive bacteria, secrete two siderophores, bacillibactin (BB) and petrobactin (PB), for iron acquisition via membrane-associated substrate-binding proteins (SBPs) and other ABC transporter components. Since PB is associated with virulence traits in B. anthracis, the PB-mediated iron uptake system presents a potential target for antimicrobial therapies; its characterization in B. cereus is described here. Separate transporters for BB, PB, and several xenosiderophores are suggested by (55)Fe-siderophore uptake studies. The PB precursor, 3,4-dihydroxybenzoic acid (3,4-DHB), and the photoproduct of FePB (FePB(nu)) also mediate iron delivery into iron-deprived cells. Putative SBPs were recombinantly expressed, and their ligand specificity and binding affinity were assessed using fluorescence spectroscopy. The noncovalent complexes of the SBPs with their respective siderophores were characterized using ESI-MS. The differences between solution phase behavior and gas phase measurements are indicative of noncovalent interactions between the siderophores and the binding sites of their respective SBPs. These studies combined with bioinformatics sequence comparison identify SBPs from five putative transporters specific for BB and enterobactin (FeuA), 3,4-DHB and PB (FatB), PB (FpuA), schizokinen (YfiY), and desferrioxamine and ferrichrome (YxeB). The two PB receptors show different substrate ranges: FatB has the highest affinity for ferric 3,4-DHB, iron-free PB, FePB, and FePB(nu), whereas FpuA is specific to only apo- and ferric PB. The biochemical characterization of these SBPs provides the first identification of the transporter candidates that most likely play a role in the B. cereus group pathogenicity.
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Affiliation(s)
- Anna M Zawadzka
- Department of Chemistry, University of California, Berkeley, 94720-1460, USA
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25
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Caiazza NC, Lies DP, Newman DK. Phototrophic Fe(II) oxidation promotes organic carbon acquisition by Rhodobacter capsulatus SB1003. Appl Environ Microbiol 2007; 73:6150-8. [PMID: 17693559 PMCID: PMC2074999 DOI: 10.1128/aem.02830-06] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 08/01/2007] [Indexed: 11/20/2022] Open
Abstract
Anoxygenic phototrophic Fe(II) oxidation is usually considered to be a lithoautotrophic metabolism that contributes to primary production in Fe-based ecosystems. In this study, we employed Rhodobacter capsulatus SB1003 as a model organism to test the hypothesis that phototrophic Fe(II) oxidation can be coupled to organic carbon acquisition. R. capsulatus SB1003 oxidized Fe(II) under anoxic conditions in a light-dependent manner, but it failed to grow lithoautotrophically on soluble Fe(II). When the strain was provided with Fe(II)-citrate, however, growth was observed that was dependent upon microbially catalyzed Fe(II) oxidation, resulting in the formation of Fe(III)-citrate. Subsequent photochemical breakdown of Fe(III)-citrate yielded acetoacetic acid that supported growth in the light but not the dark. The deletion of genes (RRC00247 and RRC00248) that encode homologs of atoA and atoD, required for acetoacetic acid utilization, severely impaired the ability of R. capsulatus SB1003 to grow on Fe(II)-citrate. The growth yield achieved by R. capsulatus SB1003 in the presence of citrate cannot be explained by lithoautotrophic growth on Fe(II) enabled by indirect effects of the ligand [such as altering the thermodynamics of Fe(II) oxidation or preventing cell encrustation]. Together, these results demonstrate that R. capsulatus SB1003 grows photoheterotrophically on Fe(II)-citrate. Nitrilotriacetic acid also supported light-dependent growth on Fe(II), suggesting that Fe(II) oxidation may be a general mechanism whereby some Fe(II)-oxidizing bacteria mine otherwise inaccessible organic carbon sources.
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Affiliation(s)
- Nicky C Caiazza
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
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26
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Pozdnyakov IP, Plyusnin VF, Tkachenko N, Lemmetyinen H. Photophysics of Fe(III)–sulfosalicylic acid complexes in aqueous solutions. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.08.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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