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Hu S, Zheng L, Zhang H, Yang Y, Chen G, Meng H, Cheng K, Guo C, Wang Y, Li X, Liu T. Sequestration of Labile Organic Matter by Secondary Fe Minerals from Chemodenitrification: Insight into Mineral Protection Mechanisms. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:11003-11015. [PMID: 38807562 DOI: 10.1021/acs.est.3c10134] [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: 05/30/2024]
Abstract
Labile organic matter (OM) immobilized by secondary iron (Fe) minerals from chemodenitrification may be an effective way to immobilize organic carbon (OC). However, the underlying mechanisms of coupled chemodenitrification and OC sequestration are poorly understood. Here, OM immobilization by secondary Fe minerals from chemodenitrification was investigated at different C/Fe ratios. Kinetics of Fe(II) oxidation and nitrite reduction rates decreased with increasing C/Fe ratios. Despite efficient sequestration, the immobilization efficiency of OM by secondary minerals varied with the C/Fe ratios. Higher C/Fe ratios were conducive to the formation of ferrihydrite and lepidocrocite, with defects and nanopores. Three contributions, including inner-core Fe-O and edge- and corner-shared Fe-Fe interactions, constituted the local coordination environment of mineral-organic composites. Microscopic analysis at the molecular scale uncovered that labile OM was more likely to combine with secondary minerals with poor crystallinity to enhance its stability, and OM distributed within nanopores and defects had a higher oxidation state. After chemodenitrification, high molecular weight substances and substances high in unsaturation or O/C ratios including phenols, polycyclic aromatics, and carboxylic compounds exhibited a stronger affinity to Fe minerals in the treatments with lower C/Fe ratios. Collectively, labile OM immobilization can occur during chemodenitrification. The findings on OM sequestration coupled with chemodenitrification have significant implications for understanding the long-term cycling of Fe, C, and N, providing a potential strategy for OM immobilization in anoxic soils and sediments.
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Affiliation(s)
- Shiwen Hu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Lirong Zheng
- Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Hanyue Zhang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, People's Republic of China
| | - Yang Yang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Guojun Chen
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Hanbing Meng
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Kuan Cheng
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Chao Guo
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Ying Wang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
| | - Xiaomin Li
- School of Environment, South China Normal University, Guangzhou 510006, China
| | - Tongxu Liu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, People's Republic of China
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Samperio-Ramos G, Hernández-Sánchez O, Camacho-Ibar VF, Pajares S, Gutiérrez A, Sandoval-Gil JM, Reyes M, De Gyves S, Balint S, Oczkowski A, Ponce-Jahen SJ, Cervantes FJ. Ammonium loss microbiologically mediated by Fe(III) and Mn(IV) reduction along a coastal lagoon system. CHEMOSPHERE 2024; 349:140933. [PMID: 38092166 DOI: 10.1016/j.chemosphere.2023.140933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 11/17/2023] [Accepted: 12/08/2023] [Indexed: 12/17/2023]
Abstract
Anaerobic ammonium oxidation, associated with both iron (Feammox) and manganese (Mnammox) reduction, is a microbial nitrogen (N) removal mechanism recently identified in natural ecosystems. Nevertheless, the spatial distributions of these non-canonical Anammox (NC-Anammox) pathways and their environmental drivers in subtidal coastal sediments are still unknown. Here, we determined the potential NC-Anammox rates and abundance of dissimilatory metal-reducing bacteria (Acidomicrobiaceae A6 and Geobacteraceae) at different horizons (0-20 cm at 5 cm intervals) of subtidal coastal sediments using the 15N isotope-tracing technique and molecular analyses. Sediments were collected across three sectors (inlet, transition, and inner) in a coastal lagoon system (Bahia de San Quintin, Mexico) dominated by seagrass meadows. The positive relationship between 30N2 production rates and dissimilatory Fe and Mn reduction provided evidence for Feammox's and Mnammox's co-occurrence. N loss through NC-Anammox was detected in subtidal sediments, with potential rates of 0.07-0.62 μg N g-1 day-1. NC-Anammox process in vegetated sediments tended to be higher than those in adjacent unvegetated ones. NC-Anammox rates showed a subsurface peak (between 5 and 15 cm) in the vegetated sediments but decreased consistently with depth in the adjacent bare bottoms. Thus, the presence/absence of seagrasses and sediment characteristics, particularly the availability of organic carbon and microbiologically reducible Fe(III) and Mn(IV), affected the abundance of dissimilatory metal-reducing bacteria, which mediated NC-Anammox activity and the associated N removal. An annual loss of 32.31 ± 3.57 t N was estimated to be associated with Feammox and Mnammox within the investigated area, accounting for 2.8-4.7% of the gross total import of reactive N from the ocean into the Bahia de San Quintin. Taken as a whole, this study reveals the distribution patterns and controlling factors of the NC-Anammox pathways along a coastal lagoon system. It improves our understanding of the coupling between N and trace metal cycles in coastal environments.
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Affiliation(s)
- Guillermo Samperio-Ramos
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico.
| | - Oscar Hernández-Sánchez
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico
| | - Víctor F Camacho-Ibar
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico
| | - Silvia Pajares
- Unidad Académica de Ecología y Biodiversidad Acuática, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Aaron Gutiérrez
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico
| | - José Miguel Sandoval-Gil
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico
| | - Mauricio Reyes
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico
| | - Sebastian De Gyves
- Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Mexico; Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico
| | - Sawyer Balint
- ORISE Participant, Atlantic Coastal Environmental Sciences Division, US Environmental Protection Agency, Narragansett, RI, USA
| | - Autumn Oczkowski
- Atlantic Coastal Environmental Sciences Division, US Environmental Protection Agency, Narragansett, RI, USA
| | - Sergio J Ponce-Jahen
- Laboratory for Research on Advanced Processes for Water Treatment, Engineering Institute, Campus Juriquilla, Universidad Nacional Autónoma de México, Mexico
| | - Francisco J Cervantes
- Laboratory for Research on Advanced Processes for Water Treatment, Engineering Institute, Campus Juriquilla, Universidad Nacional Autónoma de México, Mexico
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Bayer T, Tomaszewski EJ, Bryce C, Kappler A, Byrne JM. Continuous cultivation of the lithoautotrophic nitrate-reducing Fe(II)-oxidizing culture KS in a chemostat bioreactor. ENVIRONMENTAL MICROBIOLOGY REPORTS 2023. [PMID: 36992623 DOI: 10.1111/1758-2229.13149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/15/2023] [Indexed: 06/19/2023]
Abstract
Laboratory-based studies on microbial Fe(II) oxidation are commonly performed for 5-10 days in small volumes with high substrate concentrations, resulting in geochemical gradients and volumetric effects caused by sampling. We used a chemostat to enable uninterrupted supply of medium and investigated autotrophic nitrate-reducing Fe(II)-oxidizing culture KS for 24 days. We analysed Fe- and N-speciation, cell-mineral associations, and the identity of minerals. Results were compared to batch systems (50 and 700 mL-static/shaken). The Fe(II) oxidation rate was highest in the chemostat with 7.57 mM Fe(II) d-1 , while the extent of oxidation was similar to the other experimental setups (average oxidation of 92% of all Fe(II)). Short-range ordered Fe(III) phases, presumably ferrihydrite, precipitated and later goethite was detected in the chemostat. The 1 mM solid phase Fe(II) remained in the chemostat, up to 15 μM of reactive nitrite was measured, and 42% of visualized cells were partially or completely mineral-encrusted, likely caused by abiotic oxidation of Fe(II) by nitrite. Despite (partial) encrustation, cells were still viable. Our results show that even with similar oxidation rates as in batch cultures, cultivating Fe(II)-oxidizing microorganisms under continuous conditions reveals the importance of reactive nitrogen intermediates on Fe(II) oxidation, mineral formation and cell-mineral interactions.
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Affiliation(s)
- Timm Bayer
- Geomicrobiology Group, Center for Applied Geoscience, University of Tuebingen, Tuebingen, Germany
| | - Elizabeth J Tomaszewski
- Geomicrobiology Group, Center for Applied Geoscience, University of Tuebingen, Tuebingen, Germany
| | - Casey Bryce
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Andreas Kappler
- Geomicrobiology Group, Center for Applied Geoscience, University of Tuebingen, Tuebingen, Germany
- Cluster of Excellence: EXC 2124: Controlling Microbes to Fight Infection, Tuebingen, Germany
| | - James M Byrne
- School of Earth Sciences, University of Bristol, Bristol, UK
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Ma H, Wang P, Thompson A, Xie Q, Zhu M, Teng HH, Fu P, Liu C, Chen C. Secondary Mineral Formation and Carbon Dynamics during FeS Oxidation in the Presence of Dissolved Organic Matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:14120-14132. [PMID: 36151962 DOI: 10.1021/acs.est.1c08727] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Iron (Fe) minerals constitute a major control on organic carbon (OC) storage in soils and sediments. While previous research has mainly targeted Fe (oxyhydr)oxides, the impact of Fe sulfides and their subsequent oxidation on OC dynamics remains unresolved in redox-fluctuating environments. Here, we investigated the impact of dissolved organic matter (DOM) on FeS oxidation and how FeS and its oxidation may alter the retention and nature of DOM. After the anoxic reaction of DOM with FeS, FeS preferentially removed high-molecular-weight and nitrogen-rich compounds and promoted the formation of aqueous sulfurized organic molecules, according to Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) analysis. When exposed to O2, FeS oxidized to nanocrystalline lepidocrocite and additional aqueous sulfurized organic compounds were generated. The presence of DOM decreased the particle size of the resulting nano-lepidocrocite based on Mössbauer spectroscopy. Following FeS oxidation, most solid-phase OC remained associated with the newly formed lepidocrocite via a monodentate chelating mechanism (based on FTIR analysis), and FeS oxidation caused only a slight increase in the solubilization of solid-phase OC. Collectively, this work highlights the under-appreciated role of Fe sulfides and their oxidation in driving OC transformation and preservation.
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Affiliation(s)
- Hua Ma
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Pinya Wang
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Aaron Thompson
- Department of Crop and Soil Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Qiaorong Xie
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Mengqiang Zhu
- Department of Ecosystem Science and Management, University of Wyoming, Laramie, Wyoming 82071, United States
| | - Henry H Teng
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Pingqing Fu
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Congqiang Liu
- School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Chunmei Chen
- School of Earth System Science, Tianjin University, Tianjin 300072, China
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Li S, Diao M, Wang S, Zhu X, Dong X, Strous M, Ji G. Distinct oxygen isotope fractionations driven by different electron donors during microbial nitrate reduction in lake sediments. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:812-821. [PMID: 35691702 DOI: 10.1111/1758-2229.13101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 05/29/2022] [Indexed: 06/15/2023]
Abstract
Microbial nitrate reduction can be driven by organic carbon oxidation, as well as by inorganic electron donors, such as reduced forms of sulfur and iron. An apparent inverse oxygen isotope fractionation effect was observed during nitrate reduction in sediment incubations from five sampling sites of a freshwater lake, Hongze Lake, China. Incubations with organic and inorganic electron donor additions were performed. Especially, the inverse oxygen isotope effect was intensified after glucose addition, whereas the incubations with sulfide and Fe2+ showed normal fractionation factors. Nitrate reductase encoding genes, napA and narG, were analysed with metagenomics. Higher napA/narG ratios were associated with higher oxygen fractionation factors. The most abundant clade (59%) of NapA in the incubation with glucose was affiliated with Rhodocyclales. In contrast, it only accounted for 8%-9% of NapA in the incubations with sulfide and Fe2+ . Differences in nitrate reductases might explain different oxygen isotope effects. Our findings also suggested that large variance of O-nitrate isotope fractionations might have to be considered in the interpretation of natural isotope records.
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Affiliation(s)
- Shengjie Li
- Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, China
- Department of Geoscience, University of Calgary, Calgary, AB, Canada
| | - Muhe Diao
- Department of Geoscience, University of Calgary, Calgary, AB, Canada
| | - Shuo Wang
- Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, China
| | - Xianfang Zhu
- Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, China
| | - Xiaoli Dong
- Department of Geoscience, University of Calgary, Calgary, AB, Canada
| | - Marc Strous
- Department of Geoscience, University of Calgary, Calgary, AB, Canada
| | - Guodong Ji
- Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, China
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Liu L, Shen RL, Zhao ZQ, Ding LJ, Cui HL, Li G, Yang YP, Duan GL, Zhu YG. How different nitrogen fertilizers affect arsenic mobility in paddy soil after straw incorporation? JOURNAL OF HAZARDOUS MATERIALS 2022; 436:129135. [PMID: 35594672 DOI: 10.1016/j.jhazmat.2022.129135] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 05/07/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
In straw return fields, nitrogen-fertilizers are added to mitigate microbial competition for nitrogen with plants. However, in arsenic (As)-contaminated paddy fields, the specific effects of different nitrogen fertilizers on As mobility after straw incorporation and the interactions among iron(Fe)/carbon(C)/nitrogen(N)/As are not well understood. In the reported microcosm experiment we monitored As-mobility as a function of different dosages of KNO3, NH4Cl and rice straw incorporation. Addition of both KNO3 and NH4Cl significantly inhibited the As mobilization induced by straw incorporation. Following the KNO3 addition, the As concentration in porewater dropped by 51-66% after 2 days of the incubation by restraining Fe reduction and enhancing Fe oxidation. High-dose NH4Cl addition reduced As in porewater by 22-43% throughout the incubation by decreasing porewater pH. High-throughput sequencing results demonstrated that KNO3 addition enriches both the denitrifying and Fe-oxidizing bacteria, while diminishing Fe-reducing bacteria; NH4Cl addition has the opposite effect on Fe-reducing bacteria. Network analysis revealed that As and Fe concentrations in porewater were positively correlated with the abundance of denitrifying and Fe-reducing bacteria. This study broadens our insight into the As biogeochemistry associated with the N/C/Fe balance in soil, which are of great significance for agronomic management and mitigation the risk of As-contaminated paddy fields.
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Affiliation(s)
- Lin Liu
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shanxi 712100, China
| | - Rui-Lin Shen
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Land Science and Technology, China University of Geosciences (Beijing), Beijing 100083, China
| | - Zhong-Qiu Zhao
- College of Land Science and Technology, China University of Geosciences (Beijing), Beijing 100083, China
| | - Long-Jun Ding
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hui-Ling Cui
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Gang Li
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu-Ping Yang
- Key Laboratory for Northern Urban Agriculture of Ministry of Agriculture and Rural Affairs, Beijing University of Agriculture, Beijing 102206, China
| | - Gui-Lan Duan
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Yong-Guan Zhu
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
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Garber AI, Cohen AB, Nealson KH, Ramírez GA, Barco RA, Enzingmüller-Bleyl TC, Gehringer MM, Merino N. Metagenomic Insights Into the Microbial Iron Cycle of Subseafloor Habitats. Front Microbiol 2021; 12:667944. [PMID: 34539592 PMCID: PMC8446621 DOI: 10.3389/fmicb.2021.667944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
Microbial iron cycling influences the flux of major nutrients in the environment (e.g., through the adsorptive capacity of iron oxides) and includes biotically induced iron oxidation and reduction processes. The ecological extent of microbial iron cycling is not well understood, even with increased sequencing efforts, in part due to limitations in gene annotation pipelines and limitations in experimental studies linking phenotype to genotype. This is particularly true for the marine subseafloor, which remains undersampled, but represents the largest contiguous habitat on Earth. To address this limitation, we used FeGenie, a database and bioinformatics tool that identifies microbial iron cycling genes and enables the development of testable hypotheses on the biogeochemical cycling of iron. Herein, we survey the microbial iron cycle in diverse subseafloor habitats, including sediment-buried crustal aquifers, as well as surficial and deep sediments. We inferred the genetic potential for iron redox cycling in 32 of the 46 metagenomes included in our analysis, demonstrating the prevalence of these activities across underexplored subseafloor ecosystems. We show that while some processes (e.g., iron uptake and storage, siderophore transport potential, and iron gene regulation) are near-universal, others (e.g., iron reduction/oxidation, siderophore synthesis, and magnetosome formation) are dependent on local redox and nutrient status. Additionally, we detected niche-specific differences in strategies used for dissimilatory iron reduction, suggesting that geochemical constraints likely play an important role in dictating the dominant mechanisms for iron cycling. Overall, our survey advances the known distribution, magnitude, and potential ecological impact of microbe-mediated iron cycling and utilization in sub-benthic ecosystems.
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Affiliation(s)
- Arkadiy I Garber
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Ashley B Cohen
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, United States
| | - Kenneth H Nealson
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
| | - Gustavo A Ramírez
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel.,College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
| | - Roman A Barco
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
| | | | - Michelle M Gehringer
- Department of Microbiology, Technical University of Kaiserslautern, Kaiserslautern, Germany
| | - Nancy Merino
- Biosciences & Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
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Brooks CN, Field EK. Orange leads to black: evaluating the efficacy of co-culturing iron-oxidizing and sulfate-reducing bacteria to discern ecological relationships. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:317-324. [PMID: 33554452 DOI: 10.1111/1758-2229.12932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 06/12/2023]
Abstract
Two global cycles, iron and sulfur, are critically interconnected in estuarine environments by microbiological actors. To this point, the methods of laboratory study of this interaction have been limited. Here we propose a methodology for co-culturing from numerous coastal environments, from the same source inocula, iron-oxidizing and sulfate-reducing bacteria. The use of same source inocula is largely beneficial to understand real-world interactions that are likely occurring in situ. Through the use of this methodology, the ecological interactions between these groups can be studied in a more controlled environment. Here, we characterize the oxygen and hydrogen sulfide concentrations using microelectrode depth profiling in the co-cultures of iron-oxidizing bacteria and sulfate-reducing bacteria. These results suggest that while oxygen drives the relationship between these organisms and sulfate-reducers are reliant on iron-oxidizers in this culture to create an anoxic environment, there is likely another environmental driver that also influences the interaction as the two remain spatially distinct, as trends in FeS precipitation changed within the anoxic zone relative to the presence of Fe(III) oxyhydroxides. Understanding the relationship between iron-oxidizing and sulfate-reducing bacteria will ultimately have implications for understanding microbial cycling in estuarine environments as well as in processes such as controlling microbially influenced corrosion.
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Affiliation(s)
- Chequita N Brooks
- Department of Biology, East Carolina University, Greenville, NC, USA
| | - Erin K Field
- Department of Biology, East Carolina University, Greenville, NC, USA
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Aerobic and anaerobic iron oxidizers together drive denitrification and carbon cycling at marine iron-rich hydrothermal vents. ISME JOURNAL 2020; 15:1271-1286. [PMID: 33328652 PMCID: PMC8114936 DOI: 10.1038/s41396-020-00849-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/06/2020] [Accepted: 11/18/2020] [Indexed: 12/02/2022]
Abstract
In principle, iron oxidation can fuel significant primary productivity and nutrient cycling in dark environments such as the deep sea. However, we have an extremely limited understanding of the ecology of iron-based ecosystems, and thus the linkages between iron oxidation, carbon cycling, and nitrate reduction. Here we investigate iron microbial mats from hydrothermal vents at Lōʻihi Seamount, Hawaiʻi, using genome-resolved metagenomics and metatranscriptomics to reconstruct potential microbial roles and interactions. Our results show that the aerobic iron-oxidizing Zetaproteobacteria are the primary producers, concentrated at the oxic mat surface. Their fixed carbon supports heterotrophs deeper in the mat, notably the second most abundant organism, Candidatus Ferristratum sp. (uncultivated gen. nov.) from the uncharacterized DTB120 phylum. Candidatus Ferristratum sp., described using nine high-quality metagenome-assembled genomes with similar distributions of genes, expressed nitrate reduction genes narGH and the iron oxidation gene cyc2 in situ and in response to Fe(II) in a shipboard incubation, suggesting it is an anaerobic nitrate-reducing iron oxidizer. Candidatus Ferristratum sp. lacks a full denitrification pathway, relying on Zetaproteobacteria to remove intermediates like nitrite. Thus, at Lōʻihi, anaerobic iron oxidizers coexist with and are dependent on aerobic iron oxidizers. In total, our work shows how key community members work together to connect iron oxidation with carbon and nitrogen cycling, thus driving the biogeochemistry of exported fluids.
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Sha NQ, Wang GH, Li YH, Bai SY. Removal of abamectin and conventional pollutants in vertical flow constructed wetlands with Fe-modified biochar. RSC Adv 2020; 10:44171-44182. [PMID: 35517164 PMCID: PMC9058508 DOI: 10.1039/d0ra08265a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Accepted: 12/01/2020] [Indexed: 01/15/2023] Open
Abstract
To improve the ability of constructed wetlands to remove abamectin (ABM) and nutrients, the influence of four different substrates on constructed wetlands was studied. Four vertical up-flow constructed wetlands (UVCWs) were established to treat simulated agricultural wastewater: CW1 (quartz sand + pebbles), CW2 (pebbles + coke), CW3 (Fe-modified biochar + pebbles + coke), and CW4 (unmodified biochar + pebbles + coke). Under different combinations of hydraulic loading and organic loading, CW3 was extremely effective at removing nitrogen compared with CW1, CW2 and CW4. We found that CW3 was the most effective at treating ABM and conventional pollutants. The highest efficiency of removal of abamectin (99%), COD (98%), NH4 +-N (65%), and TP (80%) was obtained in CW3. These results were directly verified by microbiological tests and microbial community analysis. The microbial diversity of CW3 and CW4 was significantly higher than those of CW1 and CW2. Fe-modified biochar provides a feasible and effective amendment for constructed wetlands to improve the nitrogen removal for C/N (2.5 : 1-5 : 1) wastewater by the ability of microbes to remove nitrogen. Fe-modified bamboo charcoal can be used in engineering as a new type of green environmental protection constructed wetland filler in the future.
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Affiliation(s)
- Nai-Qing Sha
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology Guilin 541004 China
| | - Guo-Hao Wang
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology Guilin 541004 China
| | - Yan-Hong Li
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology Guilin 541004 China .,Collaborative Innovation Center for Water Pollution Control and Water Safety in Karst Area, Guilin University of Technology Guilin 541004 China
| | - Shao-Yuan Bai
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology Guilin 541004 China .,Collaborative Innovation Center for Water Pollution Control and Water Safety in Karst Area, Guilin University of Technology Guilin 541004 China
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11
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Zhao S, Jin Q, Sheng Y, Agrawal A, Guo D, Dong H. Promotion of Microbial Oxidation of Structural Fe(II) in Nontronite by Oxalate and NTA. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13026-13035. [PMID: 32845130 DOI: 10.1021/acs.est.0c03702] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Iron redox cycling occurs extensively in soils and sediments. Previous research has focused on microbially mediated redox cycling of aqueous Fe. At circumneutral pH, most Fe occurs in solid phase, where Fe and organic ligands interact closely. However, the role of organic ligands in microbial oxidation of solid-phase Fe(II) is not well understood. Here, we incubated reduced nontronite NAu-2 (rNAu-2) with an iron-oxidizing bacterium and in the presence of oxalate and nitrilotriacetic acid. These ligands significantly enhanced the rate and extent of microbial oxidation of structural Fe(II) in rNAu-2. Aqueous and solid-phase analyses, coupled with biogeochemical modeling, revealed a pathway for ligand-enhanced bio-oxidation of solid-phase Fe(II): (1) dissolution of rNAu-2 to form aqueous Fe(II)-ligand complex; (2) bio-oxidation to Fe(III)-ligand complex; (3) rapid reduction of Fe(III)-ligand complex to Fe(II)-ligand complex by structural Fe(II) in rNAu-2. In this process, the Fe(II)-ligand and Fe(III)-ligand complexes effectively serve as electron shuttle to expand the bioavailable pool of solid-phase Fe(II). These results have important implications for a better understanding of the bioavailability and reactivity of solid-phase Fe pool in the environment.
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Affiliation(s)
- Simin Zhao
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
| | - Qusheng Jin
- Department of Earth Sciences, University of Oregon, Eugene, Oregon 97403, United States
| | - Yizhi Sheng
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
| | - Abinash Agrawal
- Department of Earth & Environmental Sciences, Wright State University, Dayton, Ohio 45435, United States
| | - Dongyi Guo
- Geomicrobiology Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Hailiang Dong
- Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio 45056, United States
- Geomicrobiology Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
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12
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Glodowska M, Stopelli E, Schneider M, Lightfoot A, Rathi B, Straub D, Patzner M, Duyen VT, Berg M, Kleindienst S, Kappler A. Role of in Situ Natural Organic Matter in Mobilizing As during Microbial Reduction of Fe III-Mineral-Bearing Aquifer Sediments from Hanoi (Vietnam). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:4149-4159. [PMID: 32157881 DOI: 10.1021/acs.est.9b07183] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Natural organic matter (NOM) can contribute to arsenic (As) mobilization as an electron donor for microbially-mediated reductive dissolution of As-bearing Fe(III) (oxyhydr)oxides. However, to investigate this process, instead of using NOM, most laboratory studies used simple fatty acids or sugars, often at relatively high concentrations. To investigate the role of relevant C sources, we therefore extracted in situ NOM from the upper aquitard (clayey silt) and lower sandy aquifer sediments in Van Phuc (Hanoi area, Vietnam), characterized its composition, and used 100-day microcosm experiments to determine the effect of in situ OM on Fe(III) mineral reduction, As mobilization, and microbial community composition. We found that OM extracted from the clayey silt (OMC) aquitard resembles young, not fully degraded plant-related material, while OM from the sandy sediments (OMS) is more bioavailable and related to microbial biomass. Although all microcosms were amended with the same amount of C (12 mg C/L), the extent of Fe(III) reduction after 100 days was the highest with acetate/lactate (43 ± 3.5% of total Fe present in the sediments) followed by OMS (28 ± 0.3%) and OMC (19 ± 0.8%). Initial Fe(III) reduction rates were also higher with acetate/lactate (0.53 mg Fe(II) in 6 days) than with OMS and OMC (0.18 and 0.08 mg Fe(II) in 6 days, respectively). Although initially more dissolved As was detected in the acetate/lactate setups, after 100 days, higher concentrations of As (8.3 ± 0.3 and 8.8 ± 0.8 μg As/L) were reached in OMC and OMS, respectively, compared to acetate/lactate-amended setups (6.3 ± 0.7 μg As/L). 16S rRNA amplicon sequence analyses revealed that acetate/lactate mainly enriched Geobacter, while in situ OM supported growth and activity of a more diverse microbial community. Our results suggest that although the in situ NOM is less efficient in stimulating microbial Fe(III) reduction than highly bioavailable acetate/lactate, it ultimately has the potential to mobilize the same amount or even more As.
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Affiliation(s)
- M Glodowska
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
| | - E Stopelli
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf CH-8600, Switzerland
| | - M Schneider
- Institute of Applied Geosciences, Karlsruhe Institute of Technology (KIT), Karlsruhe 76131, Germany
| | - A Lightfoot
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf CH-8600, Switzerland
| | - B Rathi
- Hydrogeology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
| | - D Straub
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
- Quantitative Biology Center (QBiC), University of Tübingen, Tübingen 72074, Germany
| | - M Patzner
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
| | - V T Duyen
- Vietnam National University, Hanoi - Key Laboratory of Analytical Technology for Environmental Quality and Food Safety Control (KLATEFOS), Hanoi 10000, Vietnam
| | - M Berg
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf CH-8600, Switzerland
| | - S Kleindienst
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
| | - A Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen 72074, Germany
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13
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Lueder U, Maisch M, Laufer K, Jo Rgensen BB, Kappler A, Schmidt C. Influence of Physical Perturbation on Fe(II) Supply in Coastal Marine Sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:3209-3218. [PMID: 32064861 DOI: 10.1021/acs.est.9b06278] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Iron (Fe) biogeochemistry in marine sediments is driven by redox transformations creating Fe(II) and Fe(III) gradients. As sediments are physically mixed by wave action or bioturbation, Fe gradients re-establish regularly. In order to identify the response of dissolved Fe(II) (Fe2+) and Fe mineral phases toward mixing processes, we performed voltammetric microsensor measurements, sequential Fe extractions, and Mössbauer spectroscopy of 12 h light-dark cycle incubated marine coastal sediment. Fe2+ decreased during 7 days of undisturbed incubation from approximately 400 to 60 μM. In the first 2-4 days of incubation, Fe2+ accumulated up to 100 μM in the top 2 mm due to Fe(III) photoreduction. After physical perturbation at day 7, Fe2+ was re-mobilized reaching concentrations of 320 μM in 30 mm depth, which decreased to below detection limit within 2 days afterward. Mössbauer spectroscopy showed that the relative abundance of metastable iron-sulfur mineral phases (FeSx) increased during initial incubation and decreased together with pyrite (FeS2) after perturbation. We show that Fe2+ mobilization in marine sediments is stimulated by chemical changes caused by physical disturbances impacting the Fe redox distribution. Our study suggests that, in addition to microbial and abiotic Fe(III) reduction, including Fe(III) photoreduction, physical mixing processes induce chemical changes providing sediments and the inhabiting microbial community with Fe2+.
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Affiliation(s)
- Ulf Lueder
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany
| | - Markus Maisch
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany
| | - Katja Laufer
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus, Denmark
- GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstraße 1-3, 24148 Kiel, Germany
| | - Bo Barker Jo Rgensen
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus, Denmark
| | - Andreas Kappler
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus, Denmark
| | - Caroline Schmidt
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany
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14
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Pelikan C, Jaussi M, Wasmund K, Seidenkrantz MS, Pearce C, Kuzyk ZZA, Herbold CW, Røy H, Kjeldsen KU, Loy A. Glacial Runoff Promotes Deep Burial of Sulfur Cycling-Associated Microorganisms in Marine Sediments. Front Microbiol 2019; 10:2558. [PMID: 31787951 PMCID: PMC6853847 DOI: 10.3389/fmicb.2019.02558] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 10/23/2019] [Indexed: 12/22/2022] Open
Abstract
Marine fjords with active glacier outlets are hot spots for organic matter burial in the sediments and subsequent microbial mineralization. Here, we investigated controls on microbial community assembly in sub-arctic glacier-influenced (GI) and non-glacier-influenced (NGI) marine sediments in the Godthåbsfjord region, south-western Greenland. We used a correlative approach integrating 16S rRNA gene and dissimilatory sulfite reductase (dsrB) amplicon sequence data over six meters of depth with biogeochemistry, sulfur-cycling activities, and sediment ages. GI sediments were characterized by comparably high sedimentation rates and had "young" sediment ages of <500 years even at 6 m sediment depth. In contrast, NGI stations reached ages of approximately 10,000 years at these depths. Sediment age-depth relationships, sulfate reduction rates (SRR), and C/N ratios were strongly correlated with differences in microbial community composition between GI and NGI sediments, indicating that age and diagenetic state were key drivers of microbial community assembly in subsurface sediments. Similar bacterial and archaeal communities were present in the surface sediments of all stations, whereas only in GI sediments were many surface taxa also abundant through the whole sediment core. The relative abundance of these taxa, including diverse Desulfobacteraceae members, correlated positively with SRRs, indicating their active contributions to sulfur-cycling processes. In contrast, other surface community members, such as Desulfatiglans, Atribacteria, and Chloroflexi, survived the slow sediment burial at NGI stations and dominated in the deepest sediment layers. These taxa are typical for the energy-limited marine deep biosphere and their relative abundances correlated positively with sediment age. In conclusion, our data suggests that high rates of sediment accumulation caused by glacier runoff and associated changes in biogeochemistry, promote persistence of sulfur-cycling activity and burial of a larger fraction of the surface microbial community into the deep subsurface.
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Affiliation(s)
- Claus Pelikan
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Austrian Polar Research Institute, Vienna, Austria
| | - Marion Jaussi
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Kenneth Wasmund
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Austrian Polar Research Institute, Vienna, Austria
| | - Marit-Solveig Seidenkrantz
- Palaeoceanography and Palaeoclimate Group, Arctic Research Centre, and iClimate Interdisciplinary Centre for Climate Change, Department of Geoscience, Aarhus University, Aarhus, Denmark
| | - Christof Pearce
- Palaeoceanography and Palaeoclimate Group, Arctic Research Centre, and iClimate Interdisciplinary Centre for Climate Change, Department of Geoscience, Aarhus University, Aarhus, Denmark
| | - Zou Zou Anna Kuzyk
- Department of Geological Sciences, Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB, Canada
| | - Craig W. Herbold
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Hans Røy
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Kasper Urup Kjeldsen
- Center for Geomicrobiology, Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Alexander Loy
- Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Austrian Polar Research Institute, Vienna, Austria
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15
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Böhnke S, Sass K, Gonnella G, Diehl A, Kleint C, Bach W, Zitoun R, Koschinsky A, Indenbirken D, Sander SG, Kurtz S, Perner M. Parameters Governing the Community Structure and Element Turnover in Kermadec Volcanic Ash and Hydrothermal Fluids as Monitored by Inorganic Electron Donor Consumption, Autotrophic CO 2 Fixation and 16S Tags of the Transcriptome in Incubation Experiments. Front Microbiol 2019; 10:2296. [PMID: 31649639 PMCID: PMC6794353 DOI: 10.3389/fmicb.2019.02296] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 09/20/2019] [Indexed: 12/01/2022] Open
Abstract
The microbial community composition and its functionality was assessed for hydrothermal fluids and volcanic ash sediments from Haungaroa and hydrothermal fluids from the Brothers volcano in the Kermadec island arc (New Zealand). The Haungaroa volcanic ash sediments were dominated by epsilonproteobacterial Sulfurovum sp. Ratios of electron donor consumption to CO2 fixation from respective sediment incubations indicated that sulfide oxidation appeared to fuel autotrophic CO2 fixation, coinciding with thermodynamic estimates predicting sulfide oxidation as the major energy source in the environment. Transcript analyses with the sulfide-supplemented sediment slurries demonstrated that Sulfurovum prevailed in the experiments as well. Hence, our sediment incubations appeared to simulate environmental conditions well suggesting that sulfide oxidation catalyzed by Sulfurovum members drive biomass synthesis in the volcanic ash sediments. For the Haungaroa fluids no inorganic electron donor and responsible microorganisms could be identified that clearly stimulated autotrophic CO2 fixation. In the Brothers hydrothermal fluids Sulfurimonas (49%) and Hydrogenovibrio/Thiomicrospira (15%) species prevailed. Respective fluid incubations exhibited highest autotrophic CO2 fixation if supplemented with iron(II) or hydrogen. Likewise catabolic energy calculations predicted primarily iron(II) but also hydrogen oxidation as major energy sources in the natural fluids. According to transcript analyses with material from the incubation experiments Thiomicrospira/Hydrogenovibrio species dominated, outcompeting Sulfurimonas. Given that experimental conditions likely only simulated environmental conditions that cause Thiomicrospira/Hydrogenovibrio but not Sulfurimonas to thrive, it remains unclear which environmental parameters determine Sulfurimonas’ dominance in the Brothers natural hydrothermal fluids.
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Affiliation(s)
- Stefanie Böhnke
- Molecular Biology of Microbial Consortia, Institute of Plant Science and Microbiology, Universität Hamburg, Hamburg, Germany
| | - Katharina Sass
- Molecular Biology of Microbial Consortia, Institute of Plant Science and Microbiology, Universität Hamburg, Hamburg, Germany
| | - Giorgio Gonnella
- Center for Bioinformatics (ZBH), Universität Hamburg, Hamburg, Germany
| | - Alexander Diehl
- Department of Geosciences, MARUM - Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Charlotte Kleint
- Department of Physics and Earth Sciences, Jacobs University Bremen, Bremen, Germany
| | - Wolfgang Bach
- Department of Geosciences, MARUM - Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Rebecca Zitoun
- Department of Chemistry, University of Otago, Dunedin, New Zealand
| | - Andrea Koschinsky
- Department of Physics and Earth Sciences, Jacobs University Bremen, Bremen, Germany
| | - Daniela Indenbirken
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Sylvia G Sander
- Department of Chemistry, University of Otago, Dunedin, New Zealand
| | - Stefan Kurtz
- Center for Bioinformatics (ZBH), Universität Hamburg, Hamburg, Germany
| | - Mirjam Perner
- Molecular Biology of Microbial Consortia, Institute of Plant Science and Microbiology, Universität Hamburg, Hamburg, Germany
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16
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Otte JM, Blackwell N, Ruser R, Kappler A, Kleindienst S, Schmidt C. N 2O formation by nitrite-induced (chemo)denitrification in coastal marine sediment. Sci Rep 2019; 9:10691. [PMID: 31366952 PMCID: PMC6668465 DOI: 10.1038/s41598-019-47172-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Accepted: 07/12/2019] [Indexed: 11/08/2022] Open
Abstract
Nitrous oxide (N2O) is a potent greenhouse gas that also contributes to stratospheric ozone depletion. Besides microbial denitrification, abiotic nitrite reduction by Fe(II) (chemodenitrification) has the potential to be an important source of N2O. Here, using microcosms, we quantified N2O formation in coastal marine sediments under typical summer temperatures. Comparison between gamma-radiated and microbially-active microcosm experiments revealed that at least 15-25% of total N2O formation was caused by chemodenitrification, whereas 75-85% of total N2O was potentially produced by microbial N-transformation processes. An increase in (chemo)denitrification-based N2O formation and associated Fe(II) oxidation caused an upregulation of N2O reductase (typical nosZ) genes and a distinct community shift to potential Fe(III)-reducers (Arcobacter), Fe(II)-oxidizers (Sulfurimonas), and nitrate/nitrite-reducing microorganisms (Marinobacter). Our study suggests that chemodenitrification contributes substantially to N2O formation from marine sediments and significantly influences the N- and Fe-cycling microbial community.
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Affiliation(s)
- Julia M Otte
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
| | - Nia Blackwell
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
| | - Reiner Ruser
- Fertilization and Soil Matter Dynamics, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
- Center for Geomicrobiology, Aarhus University, Aarhus, Denmark.
| | - Sara Kleindienst
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
| | - Caroline Schmidt
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany
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17
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Bryce C, Blackwell N, Schmidt C, Otte J, Huang YM, Kleindienst S, Tomaszewski E, Schad M, Warter V, Peng C, Byrne JM, Kappler A. Microbial anaerobic Fe(II) oxidation - Ecology, mechanisms and environmental implications. Environ Microbiol 2018; 20:3462-3483. [DOI: 10.1111/1462-2920.14328] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 06/15/2018] [Accepted: 06/16/2018] [Indexed: 11/30/2022]
Affiliation(s)
- Casey Bryce
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Nia Blackwell
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | | | - Julia Otte
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Yu-Ming Huang
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | | | | | - Manuel Schad
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Viola Warter
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Chao Peng
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - James M. Byrne
- Geomicrobiology; University of Tübingen; Tübingen Germany
| | - Andreas Kappler
- Geomicrobiology; University of Tübingen; Tübingen Germany
- Center for Geomicrobiology, Department of Bioscience; Aarhus University; Aarhus Denmark
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18
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Otte JM, Blackwell N, Soos V, Rughöft S, Maisch M, Kappler A, Kleindienst S, Schmidt C. Sterilization impacts on marine sediment---Are we able to inactivate microorganisms in environmental samples? FEMS Microbiol Ecol 2018; 94:5104375. [DOI: 10.1093/femsec/fiy189] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 09/18/2018] [Indexed: 12/20/2022] Open
Affiliation(s)
- Julia M Otte
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Nia Blackwell
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Viktoria Soos
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Saskia Rughöft
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Markus Maisch
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
- Geomicrobiology, Center for Geomicrobiology, Aarhus University, Ny Munkegade 116, 8000 Aarhus, Denmark
| | - Sara Kleindienst
- Microbial Ecology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
| | - Caroline Schmidt
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Hölderlinstrasse 12, 72074 Tübingen, Germany
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19
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Koeksoy E, Halama M, Hagemann N, Weigold PR, Laufer K, Kleindienst S, Byrne JM, Sundman A, Hanselmann K, Halevy I, Schoenberg R, Konhauser KO, Kappler A. A case study for late Archean and Proterozoic biogeochemical iron- and sulphur cycling in a modern habitat-the Arvadi Spring. GEOBIOLOGY 2018; 16:353-368. [PMID: 29885273 DOI: 10.1111/gbi.12293] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 03/10/2018] [Indexed: 06/08/2023]
Abstract
As a consequence of Earth's surface oxygenation, ocean geochemistry changed from ferruginous (iron(II)-rich) into more complex ferro-euxinic (iron(II)-sulphide-rich) conditions during the Paleoproterozoic. This transition must have had profound implications for the Proterozoic microbial community that existed within the ocean water and bottom sediment; in particular, iron-oxidizing bacteria likely had to compete with emerging sulphur-metabolizers. However, the nature of their coexistence and interaction remains speculative. Here, we present geochemical and microbiological data from the Arvadi Spring in the eastern Swiss Alps, a modern model habitat for ferro-euxinic transition zones in late Archean and Proterozoic oceans during high-oxygen intervals, which enables us to reconstruct the microbial community structure in respective settings for this geological era. The spring water is oxygen-saturated but still contains relatively elevated concentrations of dissolved iron(II) (17.2 ± 2.8 μM) and sulphide (2.5 ± 0.2 μM) with simultaneously high concentrations of sulphate (8.3 ± 0.04 mM). Solids consisting of quartz, calcite, dolomite and iron(III) oxyhydroxide minerals as well as sulphur-containing particles, presumably elemental S0 , cover the spring sediment. Cultivation-based most probable number counts revealed microaerophilic iron(II)-oxidizers and sulphide-oxidizers to represent the largest fraction of iron- and sulphur-metabolizers in the spring, coexisting with less abundant iron(III)-reducers, sulphate-reducers and phototrophic and nitrate-reducing iron(II)-oxidizers. 16S rRNA gene 454 pyrosequencing showed sulphide-oxidizing Thiothrix species to be the dominating genus, supporting the results from our cultivation-based assessment. Collectively, our results suggest that anaerobic and microaerophilic iron- and sulphur-metabolizers could have coexisted in oxygenated ferro-sulphidic transition zones of late Archean and Proterozoic oceans, where they would have sustained continuous cycling of iron and sulphur compounds.
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Affiliation(s)
- Elif Koeksoy
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - Maximilian Halama
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - Nikolas Hagemann
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - Pascal R Weigold
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - Katja Laufer
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
- Bioscience, Center for Geomicrobiology, Aarhus University, Aarhus, Denmark
| | - Sara Kleindienst
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - James M Byrne
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | - Anneli Sundman
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
| | | | - Itay Halevy
- Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Ronny Schoenberg
- Isotope Geochemistry, University of Tuebingen, Tuebingen, Germany
| | - Kurt O Konhauser
- Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tuebingen, Tuebingen, Germany
- Bioscience, Center for Geomicrobiology, Aarhus University, Aarhus, Denmark
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Peng C, Sundman A, Bryce C, Catrouillet C, Borch T, Kappler A. Oxidation of Fe(II)-Organic Matter Complexes in the Presence of the Mixotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacterium Acidovorax sp. BoFeN1. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:5753-5763. [PMID: 29671587 DOI: 10.1021/acs.est.8b00953] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fe(II)-organic matter (Fe(II)-OM) complexes are abundant in the environment and may play a key role for the behavior of Fe and pollutants. Mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOx) reduce nitrate coupled to the oxidation of organic compounds and Fe(II). Fe(II) oxidation may occur enzymatically or abiotically by reaction with nitrite that forms during heterotrophic denitrification. However, it is unknown whether Fe(II)-OM complexes can be oxidized by NRFeOx. We used cell-suspension experiments with the mixotrophic nitrate-reducing Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1 to reveal the role of nonorganically bound Fe(II) (aqueous Fe(II)) and nitrite for the rates and extent of oxidation of Fe(II)-OM complexes (Fe(II)-citrate, Fe(II)-EDTA, Fe(II)-humic acid, and Fe(II)-fulvic acid). We found that Fe(II)-OM complexation inhibited microbial nitrate-reducing Fe(II) oxidation; large colloidal and negatively charged complexes showed lower oxidation rates than aqueous Fe(II). Accumulation of nitrite and fast abiotic oxidation of Fe(II)-OM complexes only happened in the presence of aqueous Fe(II) that probably interacted with (nitrite-reducing) enzymes in the periplasm causing nitrite accumulation in the periplasm and outside of the cells, whereas Fe(II)-OM complexes probably could not enter the periplasm and cause nitrite accumulation. These results suggest that Fe(II) oxidation by mixotrophic nitrate reducers in the environment depends on Fe(II) speciation, and that aqueous Fe(II) potentially plays a critical role in regulating microbial denitrification processes.
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Affiliation(s)
- Chao Peng
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | - Anneli Sundman
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | - Casey Bryce
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | | | - Thomas Borch
- Department of Soil and Crop Sciences , Colorado State University , Fort Collins , Colorado 80523 , United States
- Department of Chemistry , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
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Microbially Mediated Coupling of Fe and N Cycles by Nitrate-Reducing Fe(II)-Oxidizing Bacteria in Littoral Freshwater Sediments. Appl Environ Microbiol 2018; 84:AEM.02013-17. [PMID: 29101195 DOI: 10.1128/aem.02013-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 10/31/2017] [Indexed: 11/20/2022] Open
Abstract
Nitrate-reducing iron(II)-oxidizing bacteria have been known for approximately 20 years. There has been much debate as to what extent the reduction of nitrate and the oxidation of ferrous iron are coupled via enzymatic pathways or via abiotic processes induced by nitrite formed by heterotrophic denitrification. The aim of the present study was to assess the coupling of nitrate reduction and iron(II) oxidation by monitoring changes in substrate concentrations, as well as in the activity of nitrate-reducing bacteria in natural littoral freshwater sediment, in response to stimulation with nitrate and iron(II). In substrate-amended microcosms, we found that the biotic oxidation of ferrous iron depended on the simultaneous microbial reduction of nitrate. Additionally, the abiotic oxidation of ferrous iron by nitrite in sterilized sediment was not fast enough to explain the iron oxidation rates observed in microbially active sediment. Furthermore, the expression levels of genes coding for enzymes crucial for nitrate reduction were in some setups stimulated by the presence of ferrous iron. These results indicate that there is a direct influence of ferrous iron on bacterial denitrification and support the hypothesis that microbial nitrate reduction is stimulated by biotic iron(II) oxidation.IMPORTANCE The coupling of nitrate reduction and Fe(II) oxidation affects the environment at a local scale, e.g., by changing nutrient or heavy metal mobility in soils due to the formation of Fe(III) minerals, as well as at a global scale, e.g., by the formation of the primary greenhouse gas nitrous oxide. Although the coupling of nitrate reduction and Fe(II) oxidation was reported 20 years ago and has been studied intensively since then, the underlying mechanisms still remain unknown. One of the main knowledge gaps is the extent of enzymatic Fe(II) oxidation coupled to nitrate reduction, which has frequently been questioned in the literature. In the present study, we provide evidence for microbially mediated nitrate-reducing Fe(II) oxidation in freshwater sediments. This evidence is based on the rates of nitrate reduction and Fe(II) oxidation determined in microcosm incubations and on the effect of iron on the expression of genes required for denitrification.
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Hamdan HZ, Salam DA, Hari AR, Semerjian L, Saikaly P. Assessment of the performance of SMFCs in the bioremediation of PAHs in contaminated marine sediments under different redox conditions and analysis of the associated microbial communities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 575:1453-1461. [PMID: 27720249 DOI: 10.1016/j.scitotenv.2016.09.232] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/17/2016] [Accepted: 09/30/2016] [Indexed: 06/06/2023]
Abstract
The biodegradation of naphthalene, 2-methylnaphthalene and phenanthrene was evaluated in marine sediment microbial fuel cells (SMFCs) under different biodegradation conditions, including sulfate reduction as a major biodegradation pathway, employment of anode as terminal electron acceptor (TEA) under inhibited sulfate reducing bacteria activity, and combined sulfate and anode usage as electron acceptors. A significant removal of naphthalene and 2-methylnaphthalene was observed at early stages of incubation in all treatments and was attributed to their high volatility. In the case of phenanthrene, a significant removal (93.83±1.68%) was measured in the closed circuit SMFCs with the anode acting as the main TEA and under combined anode and sulfate reduction conditions (88.51±1.3%). A much lower removal (40.37±3.24%) was achieved in the open circuit SMFCs operating with sulfate reduction as a major biodegradation pathway. Analysis of the anodic bacterial community using 16S rRNA gene pyrosequencing revealed the enrichment of genera with potential exoelectrogenic capability, namely Geoalkalibacter and Desulfuromonas, on the anode of the closed circuit SMFCs under inhibited SRB activity, while they were not detected on the anode of open circuit SMFCs. These results demonstrate the role of the anode in enhancing PAHs biodegradation in contaminated marine sediments and suggest a higher system efficiency in the absence of competition between microbial redox processes (under SRB inhibition), namely due to the anode enrichment with exoelectrogenic bacteria, which is a more energetically favorable mechanism for PAHs oxidation than sulfate.
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Affiliation(s)
- Hamdan Z Hamdan
- Department of Civil and Environmental Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut, Lebanon
| | - Darine A Salam
- Department of Civil and Environmental Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut, Lebanon.
| | - Ananda Rao Hari
- Division of Biological and Environmental Sciences and Engineering, Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Lucy Semerjian
- Department of Environmental Health Sciences, College of Health Sciences, University of Sharjah, Sharjah, UAE
| | - Pascal Saikaly
- Division of Biological and Environmental Sciences and Engineering, Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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Evidence for the Existence of Autotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacteria in Marine Coastal Sediment. Appl Environ Microbiol 2016; 82:6120-6131. [PMID: 27496777 PMCID: PMC5068159 DOI: 10.1128/aem.01570-16] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 08/02/2016] [Indexed: 11/23/2022] Open
Abstract
Nitrate-reducing Fe(II)-oxidizing microorganisms were described for the first time ca. 20 years ago. Most pure cultures of nitrate-reducing Fe(II) oxidizers can oxidize Fe(II) only under mixotrophic conditions, i.e., when an organic cosubstrate is provided. A small number of nitrate-reducing Fe(II)-oxidizing cultures have been proposed to grow autotrophically, but unambiguous evidence for autotrophy has not always been provided. Thus, it is still unclear whether or to what extent Fe(II) oxidation coupled to nitrate reduction is an enzymatically catalyzed and energy-yielding autotrophic process or whether Fe(II) is abiotically oxidized by nitrite from heterotrophic nitrate reduction. The aim of the present study was to find evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. Microcosm incubations showed that with increasing incubation times, the stoichiometric ratio of reduced nitrate/oxidized Fe(II) [NO3−reduced/Fe(II)oxidized] decreased, indicating a decreasing contribution of heterotrophic denitrification and/or an increasing contribution of autotrophic nitrate-reducing Fe(II) oxidation over time. After incubations of sediment slurries for >10 weeks, nitrate-reducing activity ceased, although nitrate was still present. This suggests that heterotrophic nitrate reduction had ceased due to the depletion of readily available organic carbon. However, after the addition of Fe(II) to these batch incubation mixtures, the nitrate-reducing activity resumed, and Fe(II) was oxidized, indicating the activity of autotrophic nitrate-reducing Fe(II) oxidizers. The concurrent reduction of 14C-labeled bicarbonate concentrations unambiguously proved that autotrophic C fixation occurred during Fe(II) oxidation and nitrate reduction. Our results clearly demonstrated that autotrophic nitrate-reducing Fe(II)-oxidizing bacteria were present in the investigated coastal marine sediments.
IMPORTANCE Twenty years after the discovery of nitrate-reducing Fe(II) oxidizers, it is still controversially discussed whether autotrophic nitrate-reducing Fe(II)-oxidizing microorganisms exist and to what extent Fe(II) oxidation in this reduction/oxidation process is enzymatically catalyzed or which role abiotic side reactions of Fe(II) with reactive N species play. Most pure cultures of nitrate-reducing Fe(II) oxidizers are mixotrophic; i.e., they need an organic cosubstrate to maintain their activity over several cultural transfers. For the few existing autotrophic isolates and enrichment cultures, either the mechanism of nitrate-reducing Fe(II) oxidation is not known or evidence for their autotrophic lifestyle is controversial. In the present study, we provide evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. The evidence is based on stoichiometries of nitrate reduction and Fe(II) oxidation determined in microcosm incubations and the incorporation of carbon from CO2 under conditions that favor the activity of nitrate-reducing Fe(II) oxidizers.
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