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Visser AN, Martin JD, Osenbrück K, Rügner H, Grathwohl P, Kappler A. In situ incubation of iron(II)-bearing minerals and Fe(0) reveals insights into metabolic flexibility of chemolithotrophic bacteria in a nitrate polluted karst aquifer. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 926:172062. [PMID: 38554974 DOI: 10.1016/j.scitotenv.2024.172062] [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: 12/04/2023] [Revised: 03/25/2024] [Accepted: 03/26/2024] [Indexed: 04/02/2024]
Abstract
Groundwater nitrate pollution is a major reason for deteriorating water quality and threatens human and animal health. Yet, mitigating groundwater contamination naturally is often complicated since most aquifers are limited in bioavailable carbon. Since metabolically flexible microbes might have advantages for survival, this study presents a detailed description and first results on our modification of the BacTrap© method, aiming to determine the prevailing microbial community's potential to utilize chemolithotrophic pathways. Our microbial trapping devices (MTDs) were amended with four different iron sources and incubated in seven groundwater monitoring wells for ∼3 months to promote growth of nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOxB) in a nitrate-contaminated karst aquifer. Phylogenetic analysis based on 16S rRNA gene sequences implies that the identity of the iron source influenced the microbial community's composition. In addition, high throughput amplicon sequencing revealed increased relative 16S rRNA gene abundances of OTUs affiliated to genera such as Thiobacillus, Rhodobacter, Pseudomonas, Albidiferax, and Sideroxydans. MTD-derived enrichments set up with Fe(II)/nitrate/acetate to isolate potential NRFeOxB, were dominated by e.g., Acidovorax spp., Paracoccus spp. and Propionivibrio spp. MTDs are a cost-effective approach for investigating microorganisms in groundwater and our data not only solidifies the MTD's capacity to provide insights into the metabolic flexibility of the aquifer's microbial community, but also substantiates its metabolic potential for anaerobic Fe(II) oxidation.
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Affiliation(s)
- Anna-Neva Visser
- GeoZentrum Nordbayern, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Germany; Department of Geosciences, University of Tübingen, Germany.
| | - Joseph D Martin
- Department of Biology, Terrestrial Ecology, University of Copenhagen, Denmark
| | - Karsten Osenbrück
- Department of Geosciences, University of Tübingen, Germany; Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany
| | - Hermann Rügner
- Department of Geosciences, University of Tübingen, Germany
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Kaplan DI, Boyanov MI, Losey NA, Lin P, Xu C, O’Loughlin EJ, Santschi PH, Xing W, Kuhne WW, Kemner KM. Uranium Biogeochemistry in the Rhizosphere of a Contaminated Wetland. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:6381-6390. [PMID: 38547454 PMCID: PMC11008245 DOI: 10.1021/acs.est.3c10481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 03/08/2024] [Accepted: 03/11/2024] [Indexed: 04/10/2024]
Abstract
The objective of this study was to determine if U sediment concentrations in a U-contaminated wetland located within the Savannah River Site, South Carolina, were greater in the rhizosphere than in the nonrhizosphere. U concentrations were as much as 1100% greater in the rhizosphere than in the nonrhizosphere fractions; however and importantly, not all paired samples followed this trend. Iron (but not C, N, or S) concentrations were significantly enriched in the rhizosphere. XAS analyses showed that in both sediment fractions, U existed as UO22+ coordinated with iron(III)-oxides and organic matter. A key difference between the two sediment fractions was that a larger proportion of U was adsorbed to Fe(III)-oxides, not organic matter, in the rhizosphere, where significantly greater total Fe concentrations and greater proportions of ferrihydrite and goethite existed. Based on 16S rRNA analyses, most bacterial sequences in both paired samples were heterotrophs, and population differences were consistent with the generally more oxidizing conditions in the rhizosphere. Finally, U was very strongly bound to the whole (unfractionated) sediments, with an average desorption Kd value (Usediment/Uaqueous) of 3972 ± 1370 (mg-U/kg)/(mg-U/L). Together, these results indicate that the rhizosphere can greatly enrich U especially in wetland areas, where roots promote the formation of reactive Fe(III)-oxides.
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Affiliation(s)
- Daniel I. Kaplan
- Savannah
River Ecology Laboratory, University of
Georgia, Aiken, South Carolina 29802, United States
| | - Maxim I. Boyanov
- Argonne
National Laboratory, Lemont, Illinois 60439, United States
- Chemical
Engineering, Bulgarian Academy of Sciences, Sofia 1040, Bulgaria
| | - Nathaniel A. Losey
- Savannah
River National Laboratory, Aiken, South Carolina 29808, United States
| | - Peng Lin
- Savannah
River Ecology Laboratory, University of
Georgia, Aiken, South Carolina 29802, United States
| | - Chen Xu
- Marine
& Coastal Environmental Science, Texas
A&M University − Galveston, Galveston, Texas 77553, United States
| | | | - Peter H. Santschi
- Marine
& Coastal Environmental Science, Texas
A&M University − Galveston, Galveston, Texas 77553, United States
| | - Wei Xing
- Savannah
River Ecology Laboratory, University of
Georgia, Aiken, South Carolina 29802, United States
| | - Wendy W. Kuhne
- Savannah
River National Laboratory, Aiken, South Carolina 29808, United States
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Anggraini TM, An S, Chung J, Kim EJ, Kwon MJ, Kim SH, Lee S. Synergetic effect of nitrate on dissolved organic carbon attenuation through dissimilatory iron reduction during aquifer storage and recovery. WATER RESEARCH 2024; 249:120954. [PMID: 38064781 DOI: 10.1016/j.watres.2023.120954] [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: 09/21/2023] [Revised: 11/22/2023] [Accepted: 11/29/2023] [Indexed: 01/03/2024]
Abstract
Aquifer storage and recovery (ASR) is a promising water management technique in terms of quantity and quality. During ASR, iron (Fe) (hydr)oxides contained in the aquifer play a crucial role as electron acceptors in attenuating dissolved organic carbon (DOC) in recharging water through dissimilatory iron reduction (DIR). Considering the preference of electron acceptors, nitrate (NO3⁻), possibly coexisting with DOC as the prior electron acceptor to Fe (hydr)oxides, might influence DIR by interrupting electron transfer. However, this phenomenon is yet to be clarified. In this study, we systematically investigated the potential effect of NO3⁻ on DOC attenuation during ASR using a series of sediment columns representing typical aquifer conditions. The results suggest that DOC attenuation could be enhanced by the presence of NO3⁻. Specifically, total DOC attenuation was notably higher than that from the stoichiometric calculation simply employing NO3⁻ as the additional electron acceptor to Fe (hydr)oxides, implying a synergetic effect of NO3⁻ in the overall reactions. X-ray photoelectron spectroscopy analyzes revealed that the Fe(II) ions released from DIR transformed the Fe (hydr)oxides into a less bioavailable form, inhibiting further DIR. In the presence of NO3⁻, however, no aqueous Fe(II) was detected, and another form of Fe (hydr)oxide appeared on the sediment surface. This may be attributed to nitrate-dependent Fe(II) oxidation (NDFO), in which Fe(II) is (re)oxidized into Fe (hydr)oxide, which is available for the subsequent DOC attenuation. These mechanisms were supported by the dominance of DIR-relevant bacteria and the growth of NDFO-related bacteria in the presence of NO3⁻.
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Affiliation(s)
- Theresia May Anggraini
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea
| | - Seongnam An
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Jaeshik Chung
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea
| | - Eun-Ju Kim
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea
| | - Man Jae Kwon
- Department of Earth and Environmental Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Sang Hyun Kim
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea.
| | - Seunghak Lee
- Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea; Graduate School of Energy and Environment (KU-KIST GREEN SCHOOL), Korea University, Seoul 02841, Republic of Korea.
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Corbera-Rubio F, Stouten GR, Bruins J, Dost SF, Merkel AY, Müller S, van Loosdrecht MCM, van Halem D, Laureni M. " Candidatus Siderophilus nitratireducens": a putative nap-dependent nitrate-reducing iron oxidizer within the new order Siderophiliales. ISME COMMUNICATIONS 2024; 4:ycae008. [PMID: 38577582 PMCID: PMC10993476 DOI: 10.1093/ismeco/ycae008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 01/03/2024] [Accepted: 01/17/2024] [Indexed: 04/06/2024]
Abstract
Nitrate leaching from agricultural soils is increasingly found in groundwater, a primary source of drinking water worldwide. This nitrate influx can potentially stimulate the biological oxidation of iron in anoxic groundwater reservoirs. Nitrate-dependent iron-oxidizing (NDFO) bacteria have been extensively studied in laboratory settings, yet their ecophysiology in natural environments remains largely unknown. To this end, we established a pilot-scale filter on nitrate-rich groundwater to elucidate the structure and metabolism of nitrate-reducing iron-oxidizing microbiomes under oligotrophic conditions mimicking natural groundwaters. The enriched community stoichiometrically removed iron and nitrate consistently with the NDFO metabolism. Genome-resolved metagenomics revealed the underlying metabolic network between the dominant iron-dependent denitrifying autotrophs and the less abundant organoheterotrophs. The most abundant genome belonged to a new Candidate order, named Siderophiliales. This new species, "Candidatus Siderophilus nitratireducens," carries genes central genes to iron oxidation (cytochrome c cyc2), carbon fixation (rbc), and for the sole periplasmic nitrate reductase (nap). Using thermodynamics, we demonstrate that iron oxidation coupled to nap based dissimilatory reduction of nitrate to nitrite is energetically favorable under realistic Fe3+/Fe2+ and NO3-/NO2- concentration ratios. Ultimately, by bridging the gap between laboratory investigations and nitrate real-world conditions, this study provides insights into the intricate interplay between nitrate and iron in groundwater ecosystems, and expands our understanding of NDFOs taxonomic diversity and ecological role.
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Affiliation(s)
| | - Gerben R Stouten
- Delft University of Technology, Stevinweg 1, 2628 CN Delft, the Netherlands
| | | | - Simon F Dost
- WMD Water Company Drenthe, Lauwers 3, 9405 BL Assen, the Netherlands
| | - Alexander Y Merkel
- Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences, 60 let Oktjabrja pr-t, 7, bld. 2, 117312 Moscow, Russia
| | - Simon Müller
- Delft University of Technology, Stevinweg 1, 2628 CN Delft, the Netherlands
| | | | - Doris van Halem
- Delft University of Technology, Stevinweg 1, 2628 CN Delft, the Netherlands
| | - Michele Laureni
- Delft University of Technology, Stevinweg 1, 2628 CN Delft, the Netherlands
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