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Cameron ES, Sanchez S, Goldman N, Blaxter ML, Finn RD. Diversity and specificity of molecular functions in cyanobacterial symbionts. Sci Rep 2024; 14:18658. [PMID: 39134591 PMCID: PMC11319675 DOI: 10.1038/s41598-024-69215-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Accepted: 08/01/2024] [Indexed: 08/15/2024] Open
Abstract
Cyanobacteria are globally occurring photosynthetic bacteria notable for their contribution to primary production and production of toxins which have detrimental ecosystem impacts. Furthermore, cyanobacteria can form mutualistic symbiotic relationships with a diverse set of eukaryotes, including land plants, aquatic plankton and fungi. Nevertheless, not all cyanobacteria are found in symbiotic associations suggesting symbiotic cyanobacteria have evolved specializations that facilitate host-interactions. Photosynthetic capabilities, nitrogen fixation, and the production of complex biochemicals are key functions provided by host-associated cyanobacterial symbionts. To explore if additional specializations are associated with such lifestyles in cyanobacteria, we have conducted comparative phylogenomics of molecular functions and of biosynthetic gene clusters (BGCs) in 984 cyanobacterial genomes. Cyanobacteria with host-associated and symbiotic lifestyles were concentrated in the family Nostocaceae, where eight monophyletic clades correspond to specific host taxa. In agreement with previous studies, symbionts are likely to provide fixed nitrogen to their eukaryotic partners, through multiple different nitrogen fixation pathways. Additionally, our analyses identified chitin metabolising pathways in cyanobacteria associated with specific host groups, while obligate symbionts had fewer BGCs. The conservation of molecular functions and BGCs between closely related symbiotic and free-living cyanobacteria suggests the potential for additional cyanobacteria to form symbiotic relationships than is currently known.
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Affiliation(s)
- Ellen S Cameron
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge, CB10 1SD, UK
- Tree of Life, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Santiago Sanchez
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge, CB10 1SD, UK
| | - Nick Goldman
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge, CB10 1SD, UK
| | - Mark L Blaxter
- Tree of Life, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Robert D Finn
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Hinxton, Cambridge, CB10 1SD, UK.
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Magain N, Miadlikowska J, Goffinet B, Goward T, Pardo-De la Hoz C, Jüriado I, Simon A, Mercado-Díaz J, Barlow T, Moncada B, Lücking R, Spielmann A, Canez L, Wang L, Nelson P, Wheeler T, Lutzoni F, Sérusiaux E. High species richness in the lichen genus Peltigera ( Ascomycota, Lecanoromycetes): 34 species in the dolichorhizoid and scabrosoid clades of section Polydactylon, including 24 new to science. PERSOONIA 2023; 51:1-88. [PMID: 38665978 PMCID: PMC11041898 DOI: 10.3767/persoonia.2023.51.01] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 10/10/2022] [Indexed: 04/28/2024]
Abstract
Applying molecular methods to fungi establishing lichenized associations with green algae or cyanobacteria has repeatedly revealed the existence of numerous phylogenetic taxa overlooked by classical taxonomic approaches. Here, we report taxonomical conclusions based on multiple species delimitation and validation analyses performed on an eight-locus dataset that includes world-wide representatives of the dolichorhizoid and scabrosoid clades in section Polydactylon of the genus Peltigera. Following the recommendations resulting from a consensus species delimitation approach and additional species validation analysis (BPP) performed in this study, we present a total of 25 species in the dolichorhizoid clade and nine in the scabrosoid clade, including respectively 18 and six species that are new to science and formally described. Additionally, one combination and three varieties (including two new to science) are proposed in the dolichorhizoid clade. The following 24 new species are described: P. appalachiensis, P. asiatica, P. borealis, P. borinquensis, P. chabanenkoae, P. clathrata, P. elixii, P. esslingeri, P. flabellae, P. gallowayi, P. hawaiiensis, P. holtanhartwigii, P. itatiaiae, P. hokkaidoensis, P. kukwae, P. massonii, P. mikado, P. nigriventris, P. orientalis, P. rangiferina, P. sipmanii, P. stanleyensis, P. vitikainenii and P. willdenowii; the following new varieties are introduced: P. kukwae var. phyllidiata and P. truculenta var. austroscabrosa; and the following new combination is introduced: P. hymenina var. dissecta. Each species from the dolichorhizoid and scabrosoid clades is morphologically and chemically described, illustrated, and characterised with ITS sequences. Identification keys are provided for the main biogeographic regions where species from the two clades occur. Morphological and chemical characters that are commonly used for species identification in the genus Peltigera cannot be applied to unambiguously recognise most molecularly circumscribed species, due to high variation of thalli formed by individuals within a fungal species, including the presence of distinct morphs in some cases, or low interspecific variation in others. The four commonly recognised morphospecies: P. dolichorhiza, P. neopolydactyla, P. pulverulenta and P. scabrosa in the dolichorhizoid and scabrosoid clades represent species complexes spread across multiple and often phylogenetically distantly related lineages. Geographic origin of specimens is often helpful for species recognition; however, ITS sequences are frequently required for a reliable identification. Citation: Magain N, Miadlikowska J, Goffinet B, et al. 2023. High species richness in the lichen genus Peltigera (Ascomycota, Lecanoromycetes): 34 species in the dolichorhizoid and scabrosoid clades of section Polydactylon, including 24 new to science. Persoonia 51: 1-88. doi: 10.3767/persoonia.2023.51.01.
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Affiliation(s)
- N. Magain
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - J. Miadlikowska
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - B. Goffinet
- Ecology and Evolutionary Biology, Unit 3043, University of Connecticut, 75 North Eagleville road, Storrs CT, 06269-3043 USA
| | - T. Goward
- Beaty Biodiversity Museum, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - C.J. Pardo-De la Hoz
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - I. Jüriado
- Institute of Ecology and Earth Sciences, University of Tartu, J. Liivi 2, Tartu 50409, Estonia; Institute of Agricultural & Environmental Sciences, Estonian University of Life Sciences, Fr. R. Kreutzwaldi 5, Tartu 51006, Estonia
| | - A. Simon
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
- Ecology and Evolutionary Biology, Unit 3043, University of Connecticut, 75 North Eagleville road, Storrs CT, 06269-3043 USA
| | - J.A. Mercado-Díaz
- Science & Education, The Field Museum, 1400 S. Lake Shore Drive, Chicago, Illinois, 60605 USA
| | - T. Barlow
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - B. Moncada
- Licenciatura en Biología, Universidad Distrital Francisco José de Caldas, Cra. 4 No. 26B-54, Torre de Laboratorios, Herbario, Bogotá, Colombia; current address: Botanischer Garten, Freie Universität Berlin, Königin-Luise-Straße 6–8, 14195 Berlin, Germany
| | - R. Lücking
- Botanischer Garten, Freie Universität Berlin, Königin-Luise-Straße 6–8, 14195 Berlin, Germany
| | - A. Spielmann
- Laboratòrio de Botanica / Liquenologia, Instituto de Biociencias, Universidade Federal de Mato Grosso do Sul, Campo Grande – MS, Brazil
| | - L. Canez
- Laboratòrio de Botanica / Liquenologia, Instituto de Biociencias, Universidade Federal de Mato Grosso do Sul, Campo Grande – MS, Brazil
| | - L.S. Wang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, CAS, Kunming 650201, China
| | - P. Nelson
- Natural and Behavioral Sciences Division, University of Maine – Fort Kent, Fort Kent, ME, USA
| | - T. Wheeler
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - F. Lutzoni
- Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708 USA
| | - E. Sérusiaux
- Evolution and Conservation Biology, InBioS Research Center, University of Liège, Sart Tilman B22, Quartier vallée 1, Chemin de la vallée 4, B-4000 Liège, Belgium
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Wang Z, Li D, Sun X, Chen H, Xiao K, Wang K. Effects of Lithology on Asymbiotic N2 Fixation in Subtropical Secondary Forests, Southwest China. Ecosystems 2023. [DOI: 10.1007/s10021-023-00824-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Quantification of biological nitrogen fixation by Mo-independent complementary nitrogenases in environmental samples with low nitrogen fixation activity. Sci Rep 2022; 12:22011. [PMID: 36539445 PMCID: PMC9768154 DOI: 10.1038/s41598-022-24860-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 11/22/2022] [Indexed: 12/24/2022] Open
Abstract
Biological nitrogen fixation (BNF) by canonical molybdenum and complementary vanadium and iron-only nitrogenase isoforms is the primary natural source of newly fixed nitrogen. Understanding controls on global nitrogen cycling requires knowledge of the isoform responsible for environmental BNF. The isotopic acetylene reduction assay (ISARA), which measures carbon stable isotope (13C/12C) fractionation between ethylene and acetylene in acetylene reduction assays, is one of the few methods that can quantify isoform-specific BNF fluxes. Application of classical ISARA has been challenging because environmental BNF activity is often too low to generate sufficient ethylene for isotopic analyses. Here we describe a high sensitivity method to measure ethylene δ13C by in-line coupling of ethylene preconcentration to gas chromatography-combustion-isotope ratio mass spectrometry (EPCon-GC-C-IRMS). Ethylene requirements in samples with 10% v/v acetylene are reduced from > 500 to ~ 20 ppmv (~ 2 ppmv with prior offline acetylene removal). To increase robustness by reducing calibration error, single nitrogenase-isoform Azotobacter vinelandii mutants and environmental sample assays rely on a common acetylene source for ethylene production. Application of the Low BNF activity ISARA (LISARA) method to low nitrogen-fixing activity soils, leaf litter, decayed wood, cryptogams, and termites indicates complementary BNF in most sample types, calling for additional studies of isoform-specific BNF.
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Chen Y, Wang Q, Zhu J, Xi Y, Zhang Q, Dai G, He N, Yu G. Atmospheric Wet Iron, Molybdenum, and Vanadium Deposition in Chinese Terrestrial Ecosystems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:12898-12905. [PMID: 36026692 DOI: 10.1021/acs.est.2c03213] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Iron (Fe), molybdenum (Mo), and vanadium (V) are the main components of the three known biological nitrogenases, which constrain nitrogen fixation and affect ecosystem productivity. Atmospheric deposition is an important pathway of these trace metals into ecosystems. Here, we explored the deposition flux, spatiotemporal pattern, and influencing factors of atmospheric wet Fe, Mo, and V deposition based on China Wet Deposition Observation Network (ChinaWD) data from 2016 to 2020. Our results showed that atmospheric wet Fe, Mo, and V deposition was 7.77 ± 7.24, 0.16 ± 0.11, and 0.13 ± 0.12 mg m-2 a-1 in Chinese terrestrial ecosystems, respectively, and revealed obvious spatial patterns but no significant annual trends. Wet Fe deposition was significantly correlated with the soil Fe content. Mo and V deposition was more affected by anthropogenic activities than Fe deposition. Wet Mo deposition was significantly affected by Mo ore reserves and waste incineration. V deposition was significantly correlated with domestic biomass burning. This study quantified wet Fe, Mo, and V deposition in China for the first time, and the implications of atmospheric trace metal deposition on biological nitrogen fixation were discussed.
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Affiliation(s)
- Yanran Chen
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qiufeng Wang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jianxing Zhu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
| | - Yue Xi
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qiongyu Zhang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Guanhua Dai
- Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Antu 133613, China
| | - Nianpeng He
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Guirui Yu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
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Contrasting bacteriome of the hornwort Leiosporoceros dussii in two nearby sites with emphasis on the hornwort-cyanobacterial symbiosis. Symbiosis 2020. [DOI: 10.1007/s13199-020-00680-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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7
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McCluskey K, Boudreault J, St-Pierre P, Perez-Gonzalez C, Chauvier A, Rizzi A, Beauregard PB, Lafontaine DA, Penedo JC. Unprecedented tunability of riboswitch structure and regulatory function by sub-millimolar variations in physiological Mg2. Nucleic Acids Res 2020; 47:6478-6487. [PMID: 31045204 PMCID: PMC6614840 DOI: 10.1093/nar/gkz316] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2019] [Revised: 04/16/2019] [Accepted: 04/18/2019] [Indexed: 02/06/2023] Open
Abstract
Riboswitches are cis-acting regulatory RNA biosensors that rival the efficiency of those found in proteins. At the heart of their regulatory function is the formation of a highly specific aptamer–ligand complex. Understanding how these RNAs recognize the ligand to regulate gene expression at physiological concentrations of Mg2+ ions and ligand is critical given their broad impact on bacterial gene expression and their potential as antibiotic targets. In this work, we used single-molecule FRET and biochemical techniques to demonstrate that Mg2+ ions act as fine-tuning elements of the amino acid-sensing lysC aptamer's ligand-free structure in the mesophile Bacillus subtilis. Mg2+ interactions with the aptamer produce encounter complexes with strikingly different sensitivities to the ligand in different, yet equally accessible, physiological ionic conditions. Our results demonstrate that the aptamer adapts its structure and folding landscape on a Mg2+-tunable scale to efficiently respond to changes in intracellular lysine of more than two orders of magnitude. The remarkable tunability of the lysC aptamer by sub-millimolar variations in the physiological concentration of Mg2+ ions suggests that some single-aptamer riboswitches have exploited the coupling of cellular levels of ligand and divalent metal ions to tightly control gene expression.
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Affiliation(s)
- Kaley McCluskey
- SUPA School of Physics and Astronomy, University of St. Andrews, Scotland KY16 9SS, UK
| | - Julien Boudreault
- Département de Biologie, Université de Sherbrooke, Québec, Canada J1K 2R1
| | - Patrick St-Pierre
- Département de Biologie, Université de Sherbrooke, Québec, Canada J1K 2R1
| | - Cibran Perez-Gonzalez
- SUPA School of Physics and Astronomy, University of St. Andrews, Scotland KY16 9SS, UK.,Centre SÈVE, Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | - Adrien Chauvier
- Département de Biologie, Université de Sherbrooke, Québec, Canada J1K 2R1
| | - Adrien Rizzi
- Département de Chimie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | - Pascale B Beauregard
- Centre SÈVE, Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | | | - J Carlos Penedo
- SUPA School of Physics and Astronomy, University of St. Andrews, Scotland KY16 9SS, UK.,Biomedical Sciences Research Complex, School of Biology, University of St. Andrews, Scotland KY16 9ST, UK
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Molybdenum threshold for ecosystem scale alternative vanadium nitrogenase activity in boreal forests. Proc Natl Acad Sci U S A 2019; 116:24682-24688. [PMID: 31727845 PMCID: PMC6900544 DOI: 10.1073/pnas.1913314116] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Biological nitrogen fixation (BNF) is responsible for large new N inputs to terrestrial ecosystems, particularly in pristine, high-latitude areas undergoing rapid global change. The most common form of nitrogenase requires molybdenum (Mo) and Mo limitation of BNF is ubiquitous. Mo-free alternative forms of nitrogenase exist, but their roles in environmental BNF have remained uncertain. This study on N2-fixing cyanolichens provides extensive field evidence, at an ecosystem scale, that vanadium (V)-based nitrogenase greatly contributes to BNF when Mo availability is limited. Mo exposure data in circumboreal forests further suggest that V-based BNF is widespread. The results showcase the resilience of BNF to micronutrient limitation and reveal strong links between the biogeochemical cycle of macronutrients and micronutrients in terrestrial ecosystems. Biological nitrogen fixation (BNF) by microorganisms associated with cryptogamic covers, such as cyanolichens and bryophytes, is a primary source of fixed nitrogen in pristine, high-latitude ecosystems. On land, low molybdenum (Mo) availability has been shown to limit BNF by the most common form of nitrogenase (Nase), which requires Mo in its active site. Vanadium (V) and iron-only Nases have been suggested as viable alternatives to countering Mo limitation of BNF; however, field data supporting this long-standing hypothesis have been lacking. Here, we elucidate the contribution of vanadium nitrogenase (V-Nase) to BNF by cyanolichens across a 600-km latitudinal transect in eastern boreal forests of North America. Widespread V-Nase activity was detected (∼15–50% of total BNF rates), with most of the activity found in the northern part of the transect. We observed a 3-fold increase of V-Nase contribution during the 20-wk growing season. By including the contribution of V-Nase to BNF, estimates of new N input by cyanolichens increase by up to 30%. We find that variability in V-based BNF is strongly related to Mo availability, and we identify a Mo threshold of ∼250 ng·glichen−1 for the onset of V-based BNF. Our results provide compelling ecosystem-scale evidence for the use of the V-Nase as a surrogate enzyme that contributes to BNF when Mo is limiting. Given widespread findings of terrestrial Mo limitation, including the carbon-rich circumboreal belt where global change is most rapid, additional consideration of V-based BNF is required in experimental and modeling studies of terrestrial biogeochemistry.
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Iron Homeostasis in Bacillus subtilis Requires Siderophore Production and Biofilm Formation. Appl Environ Microbiol 2019; 85:AEM.02439-18. [PMID: 30446551 PMCID: PMC6344612 DOI: 10.1128/aem.02439-18] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 11/07/2018] [Indexed: 12/05/2022] Open
Abstract
Iron acquisition is of fundamental importance for microorganisms, since this metal is generally poorly bioavailable under natural conditions. In the environment, most bacteria are found tightly packed within multicellular communities named biofilms. Here, using the soil Gram-positive bacterium Bacillus subtilis, we show that biofilm formation and the production of siderophores, i.e., small molecules specifically binding metals, are both essential to ensure Fe uptake from the medium and maintain cellular Fe homeostasis. The biofilm matrix appears to play an important role favoring the efficient usage of siderophores. Taken together, our results demonstrate a close link between biofilm formation and iron acquisition in B. subtilis, allowing a better comprehension of how bacteria can cope with metal limitation under environmental conditions. Iron (Fe) is the most important metal in biology. Despite its abundance, Fe is mostly present as a ferric form in soils, strongly limiting its bioavailability. To overcome the challenge of Fe acquisition, many microorganisms produce siderophores to retrieve Fe from natural sources. Another ubiquitous feature of bacteria in natural environments is biofilm formation. Previous studies showed that external Fe strongly influenced biofilm formation in several bacteria, suggesting that this microenvironment plays a mechanistic role in micronutrient acquisition for bacteria. Here, we applied a complementary set of analytical methods and deletion mutants to evaluate the role of biofilm formation, siderophore production, and their interaction in Fe homeostasis in Bacillus subtilis. We observed that Fe homeostasis, i.e., active growth at a constant intracellular Fe concentration, requires both siderophore production and biofilm formation. Also, we report that in B. subtilis, both biofilm formation and siderophore production are required to achieve active Fe acquisition from the medium and to sustain normal growth. Furthermore, we provide evidence that the formation of biofilm slightly enhances the kinetics of Fe complexation by catechol siderophores and markedly improves siderophore use efficiency. These results provide new perspectives on the mechanism underlying siderophore-based acquisition of Fe in biofilm-forming bacteria. IMPORTANCE Iron acquisition is of fundamental importance for microorganisms, since this metal is generally poorly bioavailable under natural conditions. In the environment, most bacteria are found tightly packed within multicellular communities named biofilms. Here, using the soil Gram-positive bacterium Bacillus subtilis, we show that biofilm formation and the production of siderophores, i.e., small molecules specifically binding metals, are both essential to ensure Fe uptake from the medium and maintain cellular Fe homeostasis. The biofilm matrix appears to play an important role favoring the efficient usage of siderophores. Taken together, our results demonstrate a close link between biofilm formation and iron acquisition in B. subtilis, allowing a better comprehension of how bacteria can cope with metal limitation under environmental conditions.
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Dynarski KA, Houlton BZ. Nutrient limitation of terrestrial free-living nitrogen fixation. THE NEW PHYTOLOGIST 2018; 217:1050-1061. [PMID: 29165820 DOI: 10.1111/nph.14905] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/18/2017] [Indexed: 05/27/2023]
Abstract
Nitrogen (N) fixation by free-living bacteria is a primary N input pathway in many ecosystems and sustains global plant productivity. Uncertainty exists over the importance of N, phosphorus (P) and molybdenum (Mo) availability in controlling free-living N fixation rates. Here, we investigate the geographic occurrence and variability of nutrient constraints to free-living N fixation in the terrestrial biosphere. We compiled data from studies measuring free-living N fixation in response to N, P and Mo fertilizers. We used meta-analysis to quantitatively determine the extent to which N, P and Mo stimulate or suppress N fixation, and if environmental variables influence the degree of nutrient limitation of N fixation. Across our compiled dataset, free-living N fixation is suppressed by N fertilization and stimulated by Mo fertilization. Additionally, free-living N fixation is stimulated by P additions in tropical forests. These findings suggest that nutrient limitation is an intrinsic property of the biochemical demands of N fixation, constraining free-living N fixation in the terrestrial biosphere. These findings have implications for understanding the causes and consequences of N limitation in coupled nutrient cycles, as well as modeling and forecasting nutrient controls over carbon-climate feedbacks.
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Affiliation(s)
- Katherine A Dynarski
- Department of Land, Air, and Water Resources, University of California, Davis, 1 Shields Ave., Davis, CA, 95616, USA
| | - Benjamin Z Houlton
- Department of Land, Air, and Water Resources, University of California, Davis, 1 Shields Ave., Davis, CA, 95616, USA
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Molybdenum-Based Diazotrophy in a Sphagnum Peatland in Northern Minnesota. Appl Environ Microbiol 2017; 83:AEM.01174-17. [PMID: 28667112 DOI: 10.1128/aem.01174-17] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 06/28/2017] [Indexed: 11/20/2022] Open
Abstract
Microbial N2 fixation (diazotrophy) represents an important nitrogen source to oligotrophic peatland ecosystems, which are important sinks for atmospheric CO2 and are susceptible to the changing climate. The objectives of this study were (i) to determine the active microbial group and type of nitrogenase mediating diazotrophy in an ombrotrophic Sphagnum-dominated peat bog (the S1 peat bog, Marcell Experimental Forest, Minnesota, USA); and (ii) to determine the effect of environmental parameters (light, O2, CO2, and CH4) on potential rates of diazotrophy measured by acetylene (C2H2) reduction and 15N2 incorporation. A molecular analysis of metabolically active microbial communities suggested that diazotrophy in surface peat was primarily mediated by Alphaproteobacteria (Bradyrhizobiaceae and Beijerinckiaceae). Despite higher concentrations of dissolved vanadium ([V] 11 nM) than molybdenum ([Mo] 3 nM) in surface peat, a combination of metagenomic, amplicon sequencing, and activity measurements indicated that Mo-containing nitrogenases dominate over the V-containing form. Acetylene reduction was only detected in surface peat exposed to light, with the highest rates observed in peat collected from hollows with the highest water contents. Incorporation of 15N2 was suppressed 90% by O2 and 55% by C2H2 and was unaffected by CH4 and CO2 amendments. These results suggest that peatland diazotrophy is mediated by a combination of C2H2-sensitive and C2H2-insensitive microbes that are more active at low concentrations of O2 and show similar activity at high and low concentrations of CH4 IMPORTANCE Previous studies indicate that diazotrophy provides an important nitrogen source and is linked to methanotrophy in Sphagnum-dominated peatlands. However, the environmental controls and enzymatic pathways of peatland diazotrophy, as well as the metabolically active microbial populations that catalyze this process, remain in question. Our findings indicate that oxygen levels and photosynthetic activity override low nutrient availability in limiting diazotrophy and that members of the Alphaproteobacteria (Rhizobiales) catalyze this process at the bog surface using the molybdenum-based form of the nitrogenase enzyme.
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Rousk K, Degboe J, Michelsen A, Bradley R, Bellenger JP. Molybdenum and phosphorus limitation of moss-associated nitrogen fixation in boreal ecosystems. THE NEW PHYTOLOGIST 2017; 214:97-107. [PMID: 27883187 DOI: 10.1111/nph.14331] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/15/2016] [Indexed: 05/27/2023]
Abstract
Biological nitrogen fixation (BNF) performed by moss-associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high-latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both. BNF in dominant mosses was measured with the acetylene reduction assay (ARA) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a 15 N2 tracer technique to assess the ARA to N2 fixation conversion ratios at our subarctic site. BNF was up to four-fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : 15 N2 ratios increased with increasing Mo additions. These findings show that N2 fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability.
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Affiliation(s)
- Kathrin Rousk
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - Jefferson Degboe
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
| | - Anders Michelsen
- Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
- Center for Permafrost (CENPERM), University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - Robert Bradley
- Département de Biologie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
| | - Jean-Philippe Bellenger
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
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13
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McRose DL, Zhang X, Kraepiel AML, Morel FMM. Diversity and Activity of Alternative Nitrogenases in Sequenced Genomes and Coastal Environments. Front Microbiol 2017; 8:267. [PMID: 28293220 PMCID: PMC5328986 DOI: 10.3389/fmicb.2017.00267] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 02/07/2017] [Indexed: 11/13/2022] Open
Abstract
The nitrogenase enzyme, which catalyzes the reduction of N2 gas to NH4+, occurs as three separate isozyme that use Mo, Fe-only, or V. The majority of global nitrogen fixation is attributed to the more efficient 'canonical' Mo-nitrogenase, whereas Fe-only and V-('alternative') nitrogenases are often considered 'backup' enzymes, used when Mo is limiting. Yet, the environmental distribution and diversity of alternative nitrogenases remains largely unknown. We searched for alternative nitrogenase genes in sequenced genomes and used PacBio sequencing to explore the diversity of canonical (nifD) and alternative (anfD and vnfD) nitrogenase amplicons in two coastal environments: the Florida Everglades and Sippewissett Marsh (MA). Genome-based searches identified an additional 25 species and 10 genera not previously known to encode alternative nitrogenases. Alternative nitrogenase amplicons were found in both Sippewissett Marsh and the Florida Everglades and their activity was further confirmed using newly developed isotopic techniques. Conserved amino acid sequences corresponding to cofactor ligands were also analyzed in anfD and vnfD amplicons, offering insight into environmental variants of these motifs. This study increases the number of available anfD and vnfD sequences ∼20-fold and allows for the first comparisons of environmental Mo-, Fe-only, and V-nitrogenase diversity. Our results suggest that alternative nitrogenases are maintained across a range of organisms and environments and that they can make important contributions to nitrogenase diversity and nitrogen fixation.
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Affiliation(s)
- Darcy L McRose
- Department of Geosciences, Princeton University, Princeton NJ, USA
| | - Xinning Zhang
- Department of Geosciences, Princeton University, Princeton NJ, USA
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14
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Darnajoux R, Zhang X, McRose DL, Miadlikowska J, Lutzoni F, Kraepiel AML, Bellenger JP. Biological nitrogen fixation by alternative nitrogenases in boreal cyanolichens: importance of molybdenum availability and implications for current biological nitrogen fixation estimates. THE NEW PHYTOLOGIST 2017; 213:680-689. [PMID: 27588707 DOI: 10.1111/nph.14166] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/26/2016] [Indexed: 05/03/2023]
Abstract
Cryptogamic species and their associated cyanobacteria have attracted the attention of biogeochemists because of their critical roles in the nitrogen cycle through symbiotic and asymbiotic biological fixation of nitrogen (BNF). BNF is mediated by the nitrogenase enzyme, which, in its most common form, requires molybdenum at its active site. Molybdenum has been reported as a limiting nutrient for BNF in many ecosystems, including tropical and temperate forests. Recent studies have suggested that alternative nitrogenases, which use vanadium or iron in place of molybdenum at their active site, might play a more prominent role in natural ecosystems than previously recognized. Here, we studied the occurrence of vanadium, the role of molybdenum availability on vanadium acquisition and the contribution of alternative nitrogenases to BNF in the ubiquitous cyanolichen Peltigera aphthosa s.l. We confirmed the use of the alternative vanadium-based nitrogenase in the Nostoc cyanobiont of these lichens and its substantial contribution to BNF in this organism. We also showed that the acquisition of vanadium is strongly regulated by the abundance of molybdenum. These findings show that alternative nitrogenase can no longer be neglected in natural ecosystems, particularly in molybdenum-limited habitats.
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Affiliation(s)
- Romain Darnajoux
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1
| | - Xinning Zhang
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
| | - Darcy L McRose
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
| | | | | | - Anne M L Kraepiel
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
| | - Jean-Philippe Bellenger
- Centre Sève, Département de Chimie, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1
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15
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Marks JA, Pett-Ridge JC, Perakis SS, Allen JL, McCune B. Response of the nitrogen-fixing lichenLobaria pulmonariato phosphorus, molybdenum, and vanadium. Ecosphere 2015. [DOI: 10.1890/es15-00140.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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16
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Abstract
Vanadium is special in at least two respects: on the one hand, the tetrahedral anion vanadate(v) is similar to the phosphate anion; vanadate can thus interact with various physiological substrates that are otherwise functionalized by phosphate. On the other hand, the transition metal vanadium can easily expand its sphere beyond tetrahedral coordination, and switch between the oxidation states +v, +iv and +iii in a physiological environment. The similarity between vanadate and phosphate may account for the antidiabetic potential of vanadium compounds with carrier ligands such as maltolate and picolinate, and also for vanadium's mediation in cardiovascular and neuronal defects. Other potential medicinal applications of more complex vanadium coordination compounds, for example in the treatment of parasitic tropical diseases, may also be rooted in the specific properties of the ligand sphere. The ease of the change in the oxidation state of vanadium is employed by prokarya (bacteria and cyanobacteria) as well as by eukarya (algae and fungi) in respiratory and enzymatic functions. Macroalgae (seaweeds), fungi, lichens and Streptomyces bacteria have available haloperoxidases, and hence enzymes that enable the 2-electron oxidation of halide X(-) with peroxide, catalyzed by a Lewis-acidic V(V) center. The X(+) species thus formed can be employed to oxidatively halogenate organic substrates, a fact with implications also for the chemical processes in the atmosphere. Vanadium-dependent nitrogenases in bacteria (Azotobacter) and cyanobacteria (Anabaena) convert N2 + H(+) to NH4(+) + H2, but are also receptive for alternative substrates such as CO and C2H2. Among the enigmas to be solved with respect to the utilization of vanadium in nature is the accumulation of V(III) by some sea squirts and fan worms, as well as the purport of the nonoxido V(IV) compound amavadin in the fly agaric.
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Affiliation(s)
- Dieter Rehder
- Chemistry Department, University of Hamburg, 20146 Hamburg, Germany.
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Chen CY, Chen ML, Chen HB, Wang H, Cramer SP, Zhou ZH. α-Hydroxy coordination of mononuclear vanadyl citrate, malate and S-citramalate with N-heterocycle ligand, implying a new protonation pathway of iron-vanadium cofactor in nitrogenase. J Inorg Biochem 2014; 141:114-120. [PMID: 25240212 PMCID: PMC5065718 DOI: 10.1016/j.jinorgbio.2014.08.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/04/2014] [Accepted: 08/04/2014] [Indexed: 11/17/2022]
Abstract
Unlike the most of α-alkoxy coordination in α-hydroxycarboxylates to vanadium, novel α-hydroxy coordination to vanadium(IV) has been observed for a series of chiral and achiral monomeric α-hydroxycarboxylato vanadyl complexes [VO(H2cit)(bpy)]·2H2O (1), [VO(Hmal)(bpy)]·H2O (2), [VO(H2cit)(phen)]·1.5H2O (3), [VO(Hmal)(phen)]·H2O (4), and [(Δ)VO(S-Hcitmal)(bpy)]·2H2O (5), [VO(H2cit)(phen)]2·6.5H2O (6), which were isolated from the reactions of vanadyl sulfate with α-hydroxycarboxylates and N-heterocycle ligands in acidic solution. The complexes feature a tridentate citrate, malate or citramalate that chelates to vanadium atom through their α-hydroxy, α-carboxy and β-carboxy groups; while the other β-carboxylic acidic group of citrate is free to participate strong hydrogen bonds with lattice water molecule. The neutral α-hydroxy group also forms strong intermolecular hydrogen bonds with water molecule and the negatively-charged α-carboxy group in the environment. The inclusion of a hydrogen ion in α-alkoxy group results in the formation of a series of neutral complexes with one less positive charge. There are two different configurations of citrate with respect to the trans-position of axial oxo group, where the complex with trans-hydroxy configuration seems more stable with less hindrance. The average bond distances of V-Ohydroxy and V-Oα-carboxy are 2.196 and 2.003Å respectively, which are comparable to the VO distance (2.15Å) of homocitrate in FeV-cofactor of V-nitrogenase. A new structural model is suggested for R-homocitrato iron vanadium cofactor as VFe7S9C(R-Hhomocit) (H4homocit=homocitric acid) with one more proton in homocitrate ligand.
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Affiliation(s)
- Can-Yu Chen
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China
| | - Mao-Long Chen
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Hong-Bin Chen
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Hongxin Wang
- Department of Chemistry, University of California, Davis, CA 95616, United States
| | - Stephen P Cramer
- Department of Chemistry, University of California, Davis, CA 95616, United States.
| | - Zhao-Hui Zhou
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; Department of Chemistry, University of California, Davis, CA 95616, United States.
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