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Kang W, Mu L, Hu X. Marine Colloids Boost Nitrogen Fixation in Trichodesmium erythraeum by Photoelectrophy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:9236-9249. [PMID: 38748855 DOI: 10.1021/acs.est.4c01849] [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: 05/29/2024]
Abstract
Nitrogen fixation by the diazotrophic cyanobacterium Trichodesmium contributes up to 50% of the bioavailable nitrogen in the ocean. N2 fixation by Trichodesmium is limited by the availability of nutrients, such as iron (Fe) and phosphorus (P). Although colloids are ubiquitous in the ocean, the effects of Fe limitation on nitrogen fixation by marine colloids (MC) and the related mechanisms are largely unexplored. In this study, we found that MC exhibit photoelectrochemical properties that boost nitrogen fixation by photoelectrophy in Trichodesmium erythraeum. MC efficiently promote photosynthesis in T. erythraeum, thus enhancing its growth. Photoexcited electrons from MC are directly transferred to the photosynthetic electron transport chain and contribute to nitrogen fixation and ammonia assimilation. Transcriptomic analysis revealed that MC significantly upregulates genes related to the electron transport chain, photosystem, and photosynthesis, which is consistent with elevated photosynthetic capacities (e.g., Fv/Fm and carboxysomes). As a result, MC increase the N2 fixation rate by 67.5-89.3%. Our findings highlight a proof-of-concept electron transfer pathway by which MC boost nitrogen fixation, broadening our knowledge on the role of ubiquitous colloids in marine nitrogen biogeochemistry.
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Affiliation(s)
- Weilu Kang
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Carbon Neutrality Interdisciplinary Science Centre, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Li Mu
- Tianjin Key Laboratory of Agro-Environment and Product Safety, Key Laboratory for Environmental Factors Controlling Agro-Product Quality Safety (Ministry of Agriculture and Rural Affairs), Institute of Agro-Environmental Protection, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China
| | - Xiangang Hu
- Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Carbon Neutrality Interdisciplinary Science Centre, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
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2
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Eichner M, Inomura K, Pierella Karlusich JJ, Shaked Y. Better together? Lessons on sociality from Trichodesmium. Trends Microbiol 2023; 31:1072-1084. [PMID: 37244772 DOI: 10.1016/j.tim.2023.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 04/30/2023] [Accepted: 05/01/2023] [Indexed: 05/29/2023]
Abstract
The N2-fixing cyanobacterium Trichodesmium is an important player in the oceanic nitrogen and carbon cycles. Trichodesmium occurs both as single trichomes and as colonies containing hundreds of trichomes. In this review, we explore the benefits and disadvantages of colony formation, considering physical, chemical, and biological effects from nanometer to kilometer scale. Showing that all major life challenges are affected by colony formation, we claim that Trichodesmium's ecological success is tightly linked to its colonial lifestyle. Microbial interactions in the microbiome, chemical gradients within the colony, interactions with particles, and elevated mobility in the water column shape a highly dynamic microenvironment. We postulate that these dynamics are key to the resilience of Trichodesmium and other colony formers in our changing environment.
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Affiliation(s)
- Meri Eichner
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic.
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | | | - Yeala Shaked
- Freddy and Nadine Herrmann Institute of Earth Sciences, Hebrew University, Jerusalem, Israel; Interuniversity Institute for Marine Sciences, Eilat, Israel
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3
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Bonnet S, Guieu C, Taillandier V, Boulart C, Bouruet-Aubertot P, Gazeau F, Scalabrin C, Bressac M, Knapp AN, Cuypers Y, González-Santana D, Forrer HJ, Grisoni JM, Grosso O, Habasque J, Jardin-Camps M, Leblond N, Le Moigne FAC, Lebourges-Dhaussy A, Lory C, Nunige S, Pulido-Villena E, Rizzo AL, Sarthou G, Tilliette C. Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean. Science 2023; 380:812-817. [PMID: 37228198 DOI: 10.1126/science.abq4654] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 04/21/2023] [Indexed: 05/27/2023]
Abstract
Iron is an essential nutrient that regulates productivity in ~30% of the ocean. Compared with deep (>2000 meter) hydrothermal activity at mid-ocean ridges that provide iron to the ocean's interior, shallow (<500 meter) hydrothermal fluids are likely to influence the surface's ecosystem. However, their effect is unknown. In this work, we show that fluids emitted along the Tonga volcanic arc (South Pacific) have a substantial impact on iron concentrations in the photic layer through vertical diffusion. This enrichment stimulates biological activity, resulting in an extensive patch of chlorophyll (360,000 square kilometers). Diazotroph activity is two to eight times higher and carbon export fluxes are two to three times higher in iron-enriched waters than in adjacent unfertilized waters. Such findings reveal a previously undescribed mechanism of natural iron fertilization in the ocean that fuels regional hotspot sinks for atmospheric CO2.
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Affiliation(s)
- Sophie Bonnet
- Aix Marseille University, Université de Toulon, CNRS, IRD, MIO Marseille, France
| | - Cécile Guieu
- Laboratoire d'Océanographie de Villefranche (LOV), Institut de la Mer de Villefranche, CNRS, Sorbonne Université, 06230 Villefranche-sur-Mer, France
| | - Vincent Taillandier
- Laboratoire d'Océanographie de Villefranche (LOV), Institut de la Mer de Villefranche, CNRS, Sorbonne Université, 06230 Villefranche-sur-Mer, France
| | - Cédric Boulart
- Adaptation et Diversité en Milieu Marin, UMR 7144 AD2M CNRS-Sorbonne Université, Station Biologique de Roscoff, 29680 Roscoff, France
| | - Pascale Bouruet-Aubertot
- Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques (LOCEAN-IPSL), Sorbonne University, CNRS-IRD-MNHN, 75005 Paris, France
| | - Frédéric Gazeau
- Laboratoire d'Océanographie de Villefranche (LOV), Institut de la Mer de Villefranche, CNRS, Sorbonne Université, 06230 Villefranche-sur-Mer, France
| | - Carla Scalabrin
- Ifremer, Univ Brest, CNRS, UMR 6538 Geo-Ocean, F-29280 Plouzané, France
| | - Matthieu Bressac
- Laboratoire d'Océanographie de Villefranche (LOV), Institut de la Mer de Villefranche, CNRS, Sorbonne Université, 06230 Villefranche-sur-Mer, France
| | - Angela N Knapp
- Department of Earth, Ocean, and Atmospheric Sciences, Florida State University, Tallahassee, FL 32306, USA
| | - Yannis Cuypers
- Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques (LOCEAN-IPSL), Sorbonne University, CNRS-IRD-MNHN, 75005 Paris, France
| | - David González-Santana
- CNRS, Univ Brest, IRD, Ifremer, UMR 6539, LEMAR, Plouzané, France
- Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas, Spain
| | - Heather J Forrer
- Department of Earth, Ocean, and Atmospheric Sciences, Florida State University, Tallahassee, FL 32306, USA
| | - Jean-Michel Grisoni
- Institut de la Mer de Villefranche, IMEV, Sorbonne Université, Villefranche-sur-Mer, France
| | - Olivier Grosso
- Aix Marseille University, Université de Toulon, CNRS, IRD, MIO Marseille, France
| | - Jérémie Habasque
- CNRS, Univ Brest, IRD, Ifremer, UMR 6539, LEMAR, Plouzané, France
| | | | - Nathalie Leblond
- Institut de la Mer de Villefranche, IMEV, Sorbonne Université, Villefranche-sur-Mer, France
| | - Frédéric A C Le Moigne
- Aix Marseille University, Université de Toulon, CNRS, IRD, MIO Marseille, France
- CNRS, Univ Brest, IRD, Ifremer, UMR 6539, LEMAR, Plouzané, France
| | | | - Caroline Lory
- Aix Marseille University, Université de Toulon, CNRS, IRD, MIO Marseille, France
| | - Sandra Nunige
- Aix Marseille University, Université de Toulon, CNRS, IRD, MIO Marseille, France
| | | | - Andrea L Rizzo
- Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, Via Alfonso Corti 12, 20133 Milano, Italy
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 4, 20126 Milan, Italy
| | | | - Chloé Tilliette
- Laboratoire d'Océanographie de Villefranche (LOV), Institut de la Mer de Villefranche, CNRS, Sorbonne Université, 06230 Villefranche-sur-Mer, France
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4
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Plesh SP, Lovvorn JR, Miller MWC. Organic matter sources and flows in tundra wetland food webs. PLoS One 2023; 18:e0286368. [PMID: 37235582 DOI: 10.1371/journal.pone.0286368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 05/15/2023] [Indexed: 05/28/2023] Open
Abstract
Arctic lowland tundra is often dominated by wetlands. As numbers and types of these wetlands change with climate warming, their invertebrate biomass and assemblages may also be affected. Increased influx of nutrients and dissolved organic matter (DOM) from thawing peat may alter the relative availability of organic matter (OM) sources, differentially affecting taxa with disparate dependence on those sources. In five shallow wetland types (<40 to 110 cm deep) and in littoral zones of deeper lakes (>150 cm), we used stable isotopes (δ13C, δ15N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, peat) to the diets of nine macroinvertebrate taxa. Living macrophytes were not distinguishable isotopically from peat that likely contributed most DOM. Within invertebrate taxa, relative OM contributions were similar among all wetland types except deeper lakes. Physidae snails consumed substantial amounts of OM from cyanobacteria. However, for all other taxa examined, microalgae were the dominant or a major OM source (39-82%, mean 59%) in all wetland types except deeper lakes (20‒62%, mean 31%). Macrophytes and macrophyte-derived peat, likely consumed mostly indirectly as DOM-supported bacteria, ranged from 18‒61% (mean 41%) of ultimate OM sources in all wetland types except deeper lakes (38-80%, mean 69%). Invertebrate consumption of microalgal C may often have involved bacterial intermediates, or a mix of algae with bacteria consuming peat-derived OM. High production of periphyton with very low δ13C values were favored by continuous daylight illuminating shallow depths, high N and P levels, and high CO2 concentrations from bacterial respiration of peat-derived DOM. Although relative OM sources were similar across wetland types except deeper lakes, total invertebrate biomass was much higher in shallow wetlands with emergent vegetation. Impacts of warming on the availability of invertebrate prey to waterbirds will likely depend not on shifts in OM sources, but more on changes in overall number or area of shallow emergent wetlands.
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Affiliation(s)
- Steven P Plesh
- School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, United States of America
| | - James R Lovvorn
- School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, United States of America
| | - Micah W C Miller
- School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, United States of America
- United States Fish and Wildlife Service, Fairbanks Fish and Wildlife Field Office, Fairbanks, Alaska, United States of America
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Blanckaert ACA, Grover R, Marcus MI, Ferrier-Pagès C. Nutrient starvation and nitrate pollution impairs the assimilation of dissolved organic phosphorus in coral-Symbiodiniaceae symbiosis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:159944. [PMID: 36351498 DOI: 10.1016/j.scitotenv.2022.159944] [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: 07/11/2022] [Revised: 10/14/2022] [Accepted: 10/31/2022] [Indexed: 06/16/2023]
Abstract
Phosphorus (P) is an essential but limiting nutrient for coral growth due to low concentrations of dissolved inorganic concentrations (DIP) in reef waters. P limitation is often exacerbated when concentrations of dissolved inorganic nitrogen (DIN) increase in the reef. To increase their access to phosphorus, corals can use organic P dissolved in seawater (DOP). They possess phosphatase enzymes that transform DOP into DIP, which can then be taken up by coral symbionts. Although the concentration of DOP in reef waters is much higher than DIP, the dependence of corals on this P source is still poorly understood, especially with different concentrations of DIN in seawater. As efforts to predict the future of corals increase, improved knowledge of the P requirements of corals living under different DIN concentrations may be key to predicting coral health. In this study, we investigated P content and phosphatase activities (PAs) in Stylophora pistillata maintained under nutrient starvation, long-term nitrogen enrichment (nitrate or ammonium at 2 μM) and short-term (few hours) nitrogen pulses. Results show that under nutrient depletion and ammonium-enriched conditions, a significant increase in PAs was observed compared to control conditions, with no change in the N:P ratio of the coral tissue. On the contrary, under nitrate enrichment, there was no increase in PAs compared to control conditions, but an increase in the N:P ratio of the coral tissue. These results suggest that under nitrate enrichment, corals were unable to increase their ability to rely on DOP and replenish their cellular P content. An increase in cellular N:P ratio is detrimental to coral health as it increases the susceptibility of coral bleaching under thermal stress. These results provide an overall view of the P requirements of corals exposed to different nutrient conditions and improve our understanding of the effects of nitrogen enrichment on corals.
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Affiliation(s)
- Alice C A Blanckaert
- Sorbonne Université, UPMC Université Paris VI, IFD-ED 129, Paris Cedex 05, France; Centre Scientifique de Monaco, Coral Ecophysiology Team, 8 Quai Antoine I(er), MC 98000, Monaco.
| | - Renaud Grover
- Centre Scientifique de Monaco, Coral Ecophysiology Team, 8 Quai Antoine I(er), MC 98000, Monaco
| | - Maria-Isabelle Marcus
- Centre Scientifique de Monaco, Coral Ecophysiology Team, 8 Quai Antoine I(er), MC 98000, Monaco
| | - Christine Ferrier-Pagès
- Centre Scientifique de Monaco, Coral Ecophysiology Team, 8 Quai Antoine I(er), MC 98000, Monaco
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6
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Harding KJ, Turk-Kubo KA, Mak EWK, Weber PK, Mayali X, Zehr JP. Cell-specific measurements show nitrogen fixation by particle-attached putative non-cyanobacterial diazotrophs in the North Pacific Subtropical Gyre. Nat Commun 2022; 13:6979. [PMID: 36379938 PMCID: PMC9666432 DOI: 10.1038/s41467-022-34585-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 10/31/2022] [Indexed: 11/16/2022] Open
Abstract
Biological nitrogen fixation is a major important source of nitrogen for low-nutrient surface oceanic waters. Nitrogen-fixing (diazotrophic) cyanobacteria are believed to be the primary contributors to this process, but the contribution of non-cyanobacterial diazotrophic organisms in oxygenated surface water, while hypothesized to be important, has yet to be demonstrated. In this study, we used simultaneous 15N-dinitrogen and 13C-bicarbonate incubations combined with nanoscale secondary ion mass spectrometry analysis to screen tens of thousands of mostly particle-associated, cell-like regions of interest collected from the North Pacific Subtropical Gyre. These dual isotope incubations allow us to distinguish between non-cyanobacterial and cyanobacterial nitrogen-fixing microorganisms and to measure putative cell-specific nitrogen fixation rates. With this approach, we detect nitrogen fixation by putative non-cyanobacterial diazotrophs in the oxygenated surface ocean, which are associated with organic-rich particles (<210 µm size fraction) at two out of seven locations sampled. When present, up to 4.1% of the analyzed particles contain at least one active putative non-cyanobacterial diazotroph. The putative non-cyanobacterial diazotroph nitrogen fixation rates (0.76 ± 1.60 fmol N cell-1 d-1) suggest that these organisms are capable of fixing dinitrogen in oxygenated surface water, at least when attached to particles, and may contribute to oceanic nitrogen fixation.
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Affiliation(s)
- Katie J Harding
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
| | | | - Peter K Weber
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Xavier Mayali
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA.
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA.
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7
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Benavides M, Bonnet S, Le Moigne FAC, Armin G, Inomura K, Hallstrøm S, Riemann L, Berman-Frank I, Poletti E, Garel M, Grosso O, Leblanc K, Guigue C, Tedetti M, Dupouy C. Sinking Trichodesmium fixes nitrogen in the dark ocean. THE ISME JOURNAL 2022; 16:2398-2405. [PMID: 35835942 PMCID: PMC9478103 DOI: 10.1038/s41396-022-01289-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/29/2022] [Accepted: 07/05/2022] [Indexed: 01/04/2023]
Abstract
The photosynthetic cyanobacterium Trichodesmium is widely distributed in the surface low latitude ocean where it contributes significantly to N2 fixation and primary productivity. Previous studies found nifH genes and intact Trichodesmium colonies in the sunlight-deprived meso- and bathypelagic layers of the ocean (200-4000 m depth). Yet, the ability of Trichodesmium to fix N2 in the dark ocean has not been explored. We performed 15N2 incubations in sediment traps at 170, 270 and 1000 m at two locations in the South Pacific. Sinking Trichodesmium colonies fixed N2 at similar rates than previously observed in the surface ocean (36-214 fmol N cell-1 d-1). This activity accounted for 40 ± 28% of the bulk N2 fixation rates measured in the traps, indicating that other diazotrophs were also active in the mesopelagic zone. Accordingly, cDNA nifH amplicon sequencing revealed that while Trichodesmium accounted for most of the expressed nifH genes in the traps, other diazotrophs such as Chlorobium and Deltaproteobacteria were also active. Laboratory experiments simulating mesopelagic conditions confirmed that increasing hydrostatic pressure and decreasing temperature reduced but did not completely inhibit N2 fixation in Trichodesmium. Finally, using a cell metabolism model we predict that Trichodesmium uses photosynthesis-derived stored carbon to sustain N2 fixation while sinking into the mesopelagic. We conclude that sinking Trichodesmium provides ammonium, dissolved organic matter and biomass to mesopelagic prokaryotes.
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Affiliation(s)
- Mar Benavides
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.
- Turing Center for Living Systems, Aix-Marseille University, 13009, Marseille, France.
| | - Sophie Bonnet
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Frédéric A C Le Moigne
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
- LEMAR, Laboratoire des Sciences de l'Environnement Marin, UMR6539, CNRS, UBO, IFREMER, IRD, 29280, Plouzané, Technopôle Brest-Iroise, France
| | - Gabrielle Armin
- Graduate School of Oceanography, University of Rhode Island, South Kingstown, RI, USA
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, South Kingstown, RI, USA
| | - Søren Hallstrøm
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Lasse Riemann
- Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Ilana Berman-Frank
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Mt, Carmel, Haifa, Israel
| | - Emilie Poletti
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Marc Garel
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Olivier Grosso
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Karine Leblanc
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Catherine Guigue
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Marc Tedetti
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Cécile Dupouy
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
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8
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Cormier M, Berard J, Bougaran G, Trueman CN, Mayor DJ, Lampitt RS, Kruger NJ, Flynn KJ, Rickaby REM. Deuterium in marine organic biomarkers: toward a new tool for quantifying aquatic mixotrophy. THE NEW PHYTOLOGIST 2022; 234:776-782. [PMID: 35133656 PMCID: PMC9310953 DOI: 10.1111/nph.18023] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/03/2022] [Indexed: 06/14/2023]
Abstract
The traditional separation between primary producers (autotrophs) and consumers (heterotrophs) at the base of the marine food web is being increasingly replaced by the paradigm that mixoplankton, planktonic protists with the nutritional ability to use both phago(hetero)trophy and photo(auto)trophy to access energy are widespread globally. Thus, many 'phytoplankton' eat, while 50% of 'protozooplankton' also perform photosynthesis. Mixotrophy may enhance primary production, biomass transfer to higher trophic levels and the efficiency of the biological pump to sequester atmospheric CO2 into the deep ocean. Although this view is gaining traction, science lacks a tool to quantify the relative contributions of autotrophy and heterotrophy in planktonic protists. This hinders our understanding of their impacts on carbon cycling within marine pelagic ecosystems. It has been shown that the hydrogen (H) isotopic signature of lipids is uniquely sensitive to heterotrophy relative to autotrophy in plants and bacteria. Here, we explored whether it is also sensitive to the trophic status in protists. The new understanding of H isotope signature of lipid biomarkers suggests it offers great potential as a novel tool for quantifying the prevalence of mixotrophy in diverse marine microorganisms and thus for investigating the implications of the 'mixoplankton' paradigm.
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Affiliation(s)
- Marc‐André Cormier
- Department of Earth SciencesUniversity of OxfordSouth Parks RoadOxfordOX1 3ANUK
| | - Jean‐Baptiste Berard
- IFREMER, Physiology and Biotechnology of Algae (PBA) Laboratoryrue de l'Ile d'Yeu, BP 21105Nantes Cedex 344311France
| | - Gaël Bougaran
- IFREMER, Physiology and Biotechnology of Algae (PBA) Laboratoryrue de l'Ile d'Yeu, BP 21105Nantes Cedex 344311France
| | - Clive N. Trueman
- Ocean and Earth ScienceNational Oceanography Centre SouthamptonUniversity of SouthamptonSouthamptonSO14 3ZHUK
| | - Daniel J. Mayor
- Ocean BiogeosciencesNational Oceanography CentreSouthamptonSO14 3ZHUK
| | | | - Nicholas J. Kruger
- Department of Plant SciencesUniversity of OxfordSouth Parks RoadOxfordOX1 3RBUK
| | - Kevin J. Flynn
- Plymouth Marine LaboratoryProspect PlacePlymouthPL1 3DHUK
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9
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Lory C, Van Wambeke F, Fourquez M, Barani A, Guieu C, Tilliette C, Marie D, Nunige S, Berman-Frank I, Bonnet S. Assessing the contribution of diazotrophs to microbial Fe uptake using a group specific approach in the Western Tropical South Pacific Ocean. ISME COMMUNICATIONS 2022; 2:41. [PMID: 37938297 PMCID: PMC9723570 DOI: 10.1038/s43705-022-00122-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 03/26/2022] [Accepted: 04/07/2022] [Indexed: 04/27/2023]
Abstract
Diazotrophs are often limited by iron (Fe) availability in the oligotrophic ocean. The Western Tropical South Pacific (WTSP) ocean has been suggested as an intense N2 fixation area due to Fe fertilizations through shallow hydrothermal activity. Yet, the Fe demand of diazotrophs in their natural habitat, where they cohabit with other microbial organisms also requiring Fe, remains unknown. Here we develop and apply a method consisting of coupling 55Fe uptake experiments with cell-sorting by flow cytometry, and provide group-specific rates of in situ Fe uptake by the microbial community in the WTSP, in addition to bulk and size fractionation rates. We reveal that the diazotrophs Crocosphaera watsonii and Trichodesmium contribute substantially to the bulk in situ Fe uptake (~33% on average over the studied area), despite being numerically less abundant compared to the rest of the planktonic community. Trichodesmium had the highest cell-specific Fe uptake rates, followed by C. watsonii, picoeukaryotes, Prochlorococcus, Synechococcus and finally heterotrophic bacteria. Calculated Fe:C quotas were higher (by 2 to 52-fold) for both studied diazotrophs compared to those of the non-diazotrophic plankton, reflecting their high intrinsic Fe demand. This translates into a diazotroph biogeographical distribution that appears to be influenced by ambient dissolved Fe concentrations in the WTSP. Despite having low cell-specific uptake rates, Prochlorococcus and heterotrophic bacteria were largely the main contributors to the bulk Fe uptake (~23% and ~12%, respectively). Overall, this group-specific approach increases our ability to examine the ecophysiological role of functional groups, including those of less abundant and/or less active microbes.
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Affiliation(s)
- C Lory
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France.
| | - F Van Wambeke
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - M Fourquez
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - A Barani
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - C Guieu
- Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, F-06230, Villefranche-sur-Mer, France
| | - C Tilliette
- Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, F-06230, Villefranche-sur-Mer, France
| | - D Marie
- Sorbonne Université, CNRS, Station Biologique de Roscoff, Roscoff, France
| | - S Nunige
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - I Berman-Frank
- Department of Marine Biology, The Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel
| | - S Bonnet
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Marseille, France.
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10
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Benavides M, Duhamel S, Van Wambeke F, Shoemaker KM, Moisander PH, Salamon E, Riemann L, Bonnet S. Dissolved organic matter stimulates N2 fixation and nifH gene expression in Trichodesmium. FEMS Microbiol Lett 2021; 367:5743415. [PMID: 32083662 DOI: 10.1093/femsle/fnaa034] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 02/20/2020] [Indexed: 12/15/2022] Open
Abstract
Mixotrophy, the combination of heterotrophic and autotrophic nutrition modes, is emerging as the rule rather than the exception in marine photosynthetic plankton. Trichodesmium, a prominent diazotroph ubiquitous in the (sub)tropical oceans, is generally considered to obtain energy via autotrophy. While the ability of Trichodesmium to use dissolved organic phosphorus when deprived of inorganic phosphorus sources is well known, the extent to which this important cyanobacterium may benefit from other dissolved organic matter (DOM) resources is unknown. Here we provide evidence of carbon-, nitrogen- and phosphorus-rich DOM molecules enhancing N2 fixation rates and nifH gene expression in natural Trichodesmium colonies collected at two stations in the western tropical South Pacific. Sampling at a third station located in the oligotrophic South Pacific Gyre revealed no Trichodesmium but showed presence of UCYN-B, although no nifH expression was detected. Our results suggest that Trichodesmium behaves mixotrophically in response to certain environmental conditions, providing them with metabolic plasticity and adding up to the view that mixotrophy is widespread among marine microbes.
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Affiliation(s)
- Mar Benavides
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Solange Duhamel
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
| | - France Van Wambeke
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Katyanne M Shoemaker
- Department of Biology, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747, USA
| | - Pia H Moisander
- Department of Biology, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747, USA
| | - Ellen Salamon
- Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Lasse Riemann
- Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Sophie Bonnet
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
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11
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Benavides M, Arístegui J. Untreated sewage outfalls do not promote Trichodesmium blooms in the coasts of the Canary Islands. Sci Rep 2020; 10:18386. [PMID: 33110228 PMCID: PMC7591472 DOI: 10.1038/s41598-020-75447-1] [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: 05/10/2020] [Accepted: 09/30/2020] [Indexed: 11/10/2022] Open
Abstract
During the summer of 2017, recurrent extensive blooms of the diazotrophic cyanobacterium Trichodesmium invaded the beaches and coastal waters of the Canary Islands, causing great social alarm. Some local media and public sectors ascribed, without any strong scientific evidence, the origin and reactivation of these blooms to untreated sewage outfalls distributed along the coasts. In order to test whether sewage outfalls could have any influence on the metabolic activity of Trichodesmium, we performed 13C and 15N2 uptake experiments with colonies experiencing three different bloom development stages, incubated both with clear seawater and sewage water from an outfall south of Gran Canaria island. Our results showed that sewage outfalls did not promote any increase in dinitrogen (N2) fixation in Trichodesmium, supporting the hypothesis that decaying blooms were generated offshore and transported shoreward by local currents and winds, accumulating mostly leeward of the islands. The combination of unusually warm seawater temperatures, enhanced and sustained stratification of the upper water column and recurrent dust deposition events would have favored the development of the Trichodesmium blooms, which lasted for at least four months.
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Affiliation(s)
- Mar Benavides
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Javier Arístegui
- Instituto de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain.
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12
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Geisler E, Bogler A, Bar-Zeev E, Rahav E. Heterotrophic Nitrogen Fixation at the Hyper-Eutrophic Qishon River and Estuary System. Front Microbiol 2020; 11:1370. [PMID: 32670236 PMCID: PMC7326945 DOI: 10.3389/fmicb.2020.01370] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 05/27/2020] [Indexed: 12/04/2022] Open
Abstract
Planktonic heterotrophic diazotrophs (N2-fixers) are widely distributed in marine and freshwater systems, yet limited information is available on their activity, especially in environments with adverse conditions for diazotrophy (e.g., N-rich and oxygenated). Here, we followed the localization and activity of heterotrophic diazotrophs in the hyper-eutrophic N-rich Qishon River—an environment previously considered to be unfavorable for diazotrophy. Our results indicate high heterotrophic N2 fixation rates (up to 6.9 nmol N L–1 d–1), which were approximately three fold higher at an upstream location (freshwater) compared to an estuary (brackish) site. Further, active heterotrophic diazotrophs were capture associated with free-floating aggregates by a newly developed immunolocalization approach. These findings provide new insights on the activity of heterotrophic diazotrophs on aggregates in environments previously considered with adverse conditions for diazotrophy. Moreover, these new insights may be applicable to other aquatic regimes worldwide with similar N-rich/oxygenated conditions that should potentially inhibit N2 fixation.
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Affiliation(s)
- Eyal Geisler
- The Zuckerberg Institute for Water Research (ZIWR), The Jacob Blaustein Institutes for Desert Research (BIDR), Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
| | - Anne Bogler
- The Zuckerberg Institute for Water Research (ZIWR), The Jacob Blaustein Institutes for Desert Research (BIDR), Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Edo Bar-Zeev
- The Zuckerberg Institute for Water Research (ZIWR), The Jacob Blaustein Institutes for Desert Research (BIDR), Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Eyal Rahav
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
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13
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Mayali X. NanoSIMS: Microscale Quantification of Biogeochemical Activity with Large-Scale Impacts. ANNUAL REVIEW OF MARINE SCIENCE 2020; 12:449-467. [PMID: 31299167 DOI: 10.1146/annurev-marine-010419-010714] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
One major objective of aquatic microbial ecology is to understand the distribution of microbial populations over space and time and in response to environmental factors. Perhaps more importantly, it is crucial to quantify how those microbial cells affect biogeochemical processes of interest, such as primary production, nitrogen cycling, or the breakdown of pollutants. One valuable approach to link microbial identity to activity is to carry out incubations with stable-isotope-labeled substrates and then quantify the isotope incorporation by individual microbial cells using nanoscale secondary ion mass spectrometry (NanoSIMS). This review summarizes recent efforts in this field, highlights novel methods, describes studies investigating rare metabolisms as well as widespread microbial activity, and hopes to provide a framework to increase the use and capabilities of NanoSIMS for microbial biogeochemical studies in the future.
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Affiliation(s)
- Xavier Mayali
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA;
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14
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Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies. ISME JOURNAL 2019; 14:399-412. [PMID: 31636364 PMCID: PMC6976679 DOI: 10.1038/s41396-019-0514-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 09/10/2019] [Accepted: 09/11/2019] [Indexed: 11/08/2022]
Abstract
Trichodesmium is an important dinitrogen (N2)-fixing cyanobacterium in marine ecosystems. Recent nucleic acid analyses indicate that Trichodesmium colonies with their diverse epibionts support various nitrogen (N) transformations beyond N2 fixation. However, rates of these transformations and concentration gradients of N compounds in Trichodesmium colonies remain largely unresolved. We combined isotope-tracer incubations, micro-profiling and numeric modelling to explore carbon fixation, N cycling processes as well as oxygen, ammonium and nitrate concentration gradients in individual field-sampled Trichodesmium colonies. Colonies were net-autotrophic, with carbon and N2 fixation occurring mostly during the day. Ten percent of the fixed N was released as ammonium after 12-h incubations. Nitrification was not detectable but nitrate consumption was high when nitrate was added. The consumed nitrate was partly reduced to ammonium, while denitrification was insignificant. Thus, the potential N transformation network was characterised by fixed N gain and recycling processes rather than denitrification. Oxygen concentrations within colonies were ~60-200% air-saturation. Moreover, our modelling predicted steep concentration gradients, with up to 6-fold higher ammonium concentrations, and nitrate depletion in the colony centre compared to the ambient seawater. These gradients created a chemically heterogeneous microenvironment, presumably facilitating diverse microbial metabolisms in millimetre-sized Trichodesmium colonies.
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15
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Benavides M, Chu Van T, Mari X. Amino acids promote black carbon aggregation and microbial colonization in coastal waters off Vietnam. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 685:527-532. [PMID: 31176973 DOI: 10.1016/j.scitotenv.2019.05.141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/10/2019] [Accepted: 05/10/2019] [Indexed: 06/09/2023]
Abstract
The combustion of fossil fuels and biomass produces pyrogenic organic matter usually known as 'black carbon' (BC), which are transported across the atmosphere as particulate aerosol, eventually deposited on land and oceans. Soil studies have investigated the potential microbial colonization and remineralization of BC particles, but this process has been seldom studied in marine waters. BC provides a significant input of organic carbon to the oceans, yet its fate and role in biogeochemical cycling remains unknown. Here we explored the microbial colonization of BC particles in coastal seawater samples collected in Halong Bay (northern Vietnam). Using high-resolution mass spectrometry and microscopy methods, we observed an increasing colonization of BC particles by marine microbes in the presence of amino acids. Our results suggest that natural organic matter (NOM) present in seawater may promote the microbial colonization and eventual remineralization of BC particles. Future experiments should explore the potential microbial remineralization of BC particles to unveil the role of this massive source of carbon to marine ecosystems.
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Affiliation(s)
- Mar Benavides
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288 Marseille, France.
| | - Thuoc Chu Van
- Institute of Marine Environment and Resources (IMER), Vietnam Academy of Science and Technology (VAST), 246 Da Nang Street, Haiphong, Viet Nam
| | - Xavier Mari
- Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288 Marseille, France; Institute of Marine Environment and Resources (IMER), Vietnam Academy of Science and Technology (VAST), 246 Da Nang Street, Haiphong, Viet Nam; University of Science and Technology of Hanoi (USTH), Vietnam Academy of Science and Technology (VAST), Hanoi, Viet Nam
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16
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Li D, Liu J, Zhang R, Chen M, Yang W, Li J, Fang Z, Wang B, Qiu Y, Zheng M. N 2 fixation impacted by carbon fixation via dissolved organic carbon in the changing Daya Bay, South China Sea. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 674:592-602. [PMID: 31022548 DOI: 10.1016/j.scitotenv.2019.04.176] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 04/11/2019] [Accepted: 04/11/2019] [Indexed: 06/09/2023]
Abstract
We present the first concurrent measurements of N2 fixation rates (15N2 uptake), primary production (14C uptake), dissolved organic carbon (DOC) concentrations, and diazotrophic community composition derived from nitrogenase (nifH) abundance in the subtropical Daya Bay (DB) of the coastal northern South China Sea (NSCS) from 2015 to 2017. N2 fixation rates ranged from n.d. - 4.51 nmol N L-1 h-1. Such values were generally higher than those reported in the neighbouring NSCS open waters and several well-studied oligotrophic waters, thereby suggesting that N-replete conditions do not prevent N2 fixation in coastal waters. N2 fixation rates were positively and significantly correlated with the primary production and the concentration of DOC in DB in the spring and summer. Combined with other lines of evidence, we suggest that N2 fixation may be facilitated by non-diazotrophic phytoplankton via a probable regulation of the quantity and quality (bioavailability) of DOC in DB. Since DB represents a suitable site that has experienced dramatic human-induced changes in environmental conditions, our results likely provide insights in understanding how N2 fixation and relevant biogeochemical processes may respond to intensified global anthropogenic forcing in similar coastal settings.
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Affiliation(s)
- Danyang Li
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Jiaxing Liu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, No. 164, West Xingang Road, Guangzhou 510301, China
| | - Run Zhang
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
| | - Min Chen
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Weifeng Yang
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China
| | - Junjie Li
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Ziming Fang
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Bo Wang
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Yusheng Qiu
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Minfang Zheng
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
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17
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Eichner M, Thoms S, Rost B, Mohr W, Ahmerkamp S, Ploug H, Kuypers MMM, de Beer D. N 2 fixation in free-floating filaments of Trichodesmium is higher than in transiently suboxic colony microenvironments. THE NEW PHYTOLOGIST 2019; 222:852-863. [PMID: 30507001 PMCID: PMC6590460 DOI: 10.1111/nph.15621] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/22/2018] [Indexed: 05/31/2023]
Abstract
To understand the role of micrometer-scale oxygen (O2 ) gradients in facilitating dinitrogen (N2 ) fixation, we characterized O2 dynamics in the microenvironment around free-floating trichomes and colonies of Trichodesmium erythraeum IMS101. Diurnal and spatial variability in O2 concentrations in the bulk medium, within colonies, along trichomes and within single cells were determined using O2 optodes, microsensors and model calculations. Carbon (C) and N2 fixation as well as O2 evolution and uptake under different O2 concentrations were analyzed by stable isotope incubations and membrane inlet mass spectrometry. We observed a pronounced diel rhythm in O2 fluxes, with net O2 evolution restricted to short periods in the morning and evening, and net O2 uptake driven by dark respiration and light-dependent O2 uptake during the major part of the light period. Remarkably, colonies showed lower N2 fixation and C fixation rates than free-floating trichomes despite the long period of O2 undersaturation in the colony microenvironment. Model calculations demonstrate that low permeability of the cell wall in combination with metabolic heterogeneity between single cells allows for anoxic intracellular conditions in colonies but also free-floating trichomes of Trichodesmium. Therefore, whereas colony formation must have benefits for Trichodesmium, it does not favor N2 fixation.
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Affiliation(s)
- Meri Eichner
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1Bremen28359Germany
| | - Silke Thoms
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchAm Handelshafen 12Bremerhaven27570Germany
| | - Björn Rost
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchAm Handelshafen 12Bremerhaven27570Germany
| | - Wiebke Mohr
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1Bremen28359Germany
| | - Soeren Ahmerkamp
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1Bremen28359Germany
| | - Helle Ploug
- Department of Marine SciencesUniversity of GothenburgCarl Skottbergsgata 22 BGöteborg41319Sweden
| | | | - Dirk de Beer
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1Bremen28359Germany
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18
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Taylor GT. Windows into Microbial Seascapes: Advances in Nanoscale Imaging and Application to Marine Sciences. ANNUAL REVIEW OF MARINE SCIENCE 2019; 11:465-490. [PMID: 30134123 DOI: 10.1146/annurev-marine-121916-063612] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Geochemical cycles of all nonconservative elements are mediated by microorganisms over nanometer spatial scales. The pelagic seascape is known to possess microstructure imposed by heterogeneous distributions of particles, polymeric gels, biologically important chemicals, and microbes. While indispensable, most traditional oceanographic observational approaches overlook this heterogeneity and ignore subtleties, such as activity hot spots, symbioses, niche partitioning, and intrapopulation phenotypic variations, that can provide a deeper mechanistic understanding of planktonic ecosystem function. As part of the movement toward cultivation-independent tools in microbial oceanography, techniques to examine the ecophysiology of individual populations and their role in chemical transformations at spatial scales relevant to microorganisms have been developed. This review presents technologies that enable geochemical and microbiological interrogations at spatial scales ranging from 0.02 to a few hundred micrometers, particularly focusing on atomic force microscopy, nanoscale secondary ion mass spectrometry, and confocal Raman microspectroscopy and introducing promising approaches for future applications in marine sciences.
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Affiliation(s)
- Gordon T Taylor
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794, USA;
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19
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Duhamel S, Van Wambeke F, Lefevre D, Benavides M, Bonnet S. Mixotrophic metabolism by natural communities of unicellular cyanobacteria in the western tropical South Pacific Ocean. Environ Microbiol 2018; 20:2743-2756. [PMID: 29573372 DOI: 10.1111/1462-2920.14111] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 03/12/2018] [Accepted: 03/17/2018] [Indexed: 12/31/2022]
Abstract
Cyanobacteria are major contributors to ocean biogeochemical cycling. However, mixotrophic metabolism and the relative importance of inorganic and organic carbon assimilation within the most abundant cyanobacteria are still poorly understood. We explore the ability of Prochlorococcus and Synechococcus to assimilate organic molecules with variable C:N:P composition and its modulation by light availability and photosynthetic impairment. We used a combination of radiolabelled molecules incubations with flow cytometry cell sorting to separate picoplankton groups from the western tropical South Pacific Ocean. Prochlorococcus and Synechococcus assimilated glucose, leucine and ATP at all stations, but cell-specific assimilation rates of N and P containing molecules were significantly higher than glucose. Incubations in the dark or with an inhibitor of photosystem II resulted in reduced assimilation rates. Light-enhanced cell-specific glucose uptake was generally higher for cyanobacteria (∼50%) than for the low nucleic acid fraction of bacterioplankton (LNA, ∼35%). Our results confirm previous findings, based mainly on cultures and genomic potentials, showing that Prochlorococcus and Synechococcus have a flexible mixotrophic metabolism, but demonstrate that natural populations remain primarily photoautotrophs. Our findings indicate that mixotrophy by marine cyanobacteria is more likely to be an adaptation to low inorganic nutrient availability rather than a facultative pathway for carbon acquisition.
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Affiliation(s)
- Solange Duhamel
- Lamont Doherty Earth Observatory, Division of Biology and Paleo Environment, PO Box 1000, 61 Route 9W, Palisades, NY 10964, USA
| | - France Van Wambeke
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Dominique Lefevre
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Mar Benavides
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.,Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 98848, Noumea, New Caledonia
| | - Sophie Bonnet
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.,Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 98848, Noumea, New Caledonia
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20
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Nutrient-Colimited Trichodesmium as a Nitrogen Source or Sink in a Future Ocean. Appl Environ Microbiol 2018; 84:AEM.02137-17. [PMID: 29180365 DOI: 10.1128/aem.02137-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/16/2017] [Indexed: 11/20/2022] Open
Abstract
Nitrogen-fixing (N2) cyanobacteria provide bioavailable nitrogen to vast ocean regions but are in turn limited by iron (Fe) and/or phosphorus (P), which may force them to employ alternative nitrogen acquisition strategies. The adaptive responses of nitrogen fixers to global-change drivers under nutrient-limited conditions could profoundly alter the current ocean nitrogen and carbon cycles. Here, we show that the globally important N2 fixer Trichodesmium fundamentally shifts nitrogen metabolism toward organic-nitrogen scavenging following long-term high-CO2 adaptation under iron and/or phosphorus (co)limitation. Global shifts in transcripts and proteins under high-CO2/Fe-limited and/or P-limited conditions include decreases in the N2-fixing nitrogenase enzyme, coupled with major increases in enzymes that oxidize trimethylamine (TMA). TMA is an abundant, biogeochemically important organic nitrogen compound that supports rapid Trichodesmium growth while inhibiting N2 fixation. In a future high-CO2 ocean, this whole-cell energetic reallocation toward organic nitrogen scavenging and away from N2 fixation may reduce new-nitrogen inputs by Trichodesmium while simultaneously depleting the scarce fixed-nitrogen supplies of nitrogen-limited open-ocean ecosystems.IMPORTANCE Trichodesmium is among the most biogeochemically significant microorganisms in the ocean, since it supplies up to 50% of the new nitrogen supporting open-ocean food webs. We used Trichodesmium cultures adapted to high-CO2 conditions for 7 years, followed by additional exposure to iron and/or phosphorus (co)limitation. We show that "future ocean" conditions of high CO2 and concurrent nutrient limitation(s) fundamentally shift nitrogen metabolism away from nitrogen fixation and instead toward upregulation of organic nitrogen-scavenging pathways. We show that the responses of Trichodesmium to projected future ocean conditions include decreases in the nitrogen-fixing nitrogenase enzymes coupled with major increases in enzymes that oxidize the abundant organic nitrogen source trimethylamine (TMA). Such a shift toward organic nitrogen uptake and away from nitrogen fixation may substantially reduce new-nitrogen inputs by Trichodesmium to the rest of the microbial community in the future high-CO2 ocean, with potential global implications for ocean carbon and nitrogen cycling.
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21
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Abstract
Secondary ion mass spectrometry (SIMS) has become an increasingly utilized tool in biologically relevant studies. Of these, high lateral resolution methodologies using the NanoSIMS 50/50L have been especially powerful within many biological fields over the past decade. Here, the authors provide a review of this technology, sample preparation and analysis considerations, examples of recent biological studies, data analyses, and current outlooks. Specifically, the authors offer an overview of SIMS and development of the NanoSIMS. The authors describe the major experimental factors that should be considered prior to NanoSIMS analysis and then provide information on best practices for data analysis and image generation, which includes an in-depth discussion of appropriate colormaps. Additionally, the authors provide an open-source method for data representation that allows simultaneous visualization of secondary electron and ion information within a single image. Finally, the authors present a perspective on the future of this technology and where they think it will have the greatest impact in near future.
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22
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Moisander PH, Benavides M, Bonnet S, Berman-Frank I, White AE, Riemann L. Chasing after Non-cyanobacterial Nitrogen Fixation in Marine Pelagic Environments. Front Microbiol 2017; 8:1736. [PMID: 28943875 PMCID: PMC5596534 DOI: 10.3389/fmicb.2017.01736] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Accepted: 08/25/2017] [Indexed: 11/22/2022] Open
Abstract
Traditionally, cyanobacterial activity in oceanic photic layers was considered responsible for the marine pelagic dinitrogen (N2) fixation. Other potentially N2-fixing bacteria and archaea have also been detected in the pelagic water column, however, the activity and importance of these non-cyanobacterial diazotrophs (NCDs) remain poorly constrained. In this perspective we summarize the N2 fixation rates from recently published studies on photic and aphotic layers that have been attributed to NCD activity via parallel molecular measurements, and discuss the status, challenges, and data gaps in estimating non-cyanobacterial N2 fixation NCNF in the ocean. Rates attributed to NCNF have generally been near the detection limit thus far (<1 nmol N L−1 d−1). Yet, if considering the large volume of the dark ocean, even low rates of NCNF could make a significant contribution to the new nitrogen input to the ocean. The synthesis here shows that nifH transcription data for NCDs have been reported in only a few studies where N2 fixation rates were detected in the absence of diazotrophic cyanobacteria. In addition, high apparent diversity and regional variability in the NCDs complicate investigations of these communities. Future studies should focus on further investigating impacts of environmental drivers including oxygen, dissolved organic matter, and dissolved inorganic nitrogen on NCNF. Describing the ecology of NCDs and accurately measuring NCNF rates, are critical for a future evaluation of the contribution of NCNF to the marine nitrogen budget.
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Affiliation(s)
- Pia H Moisander
- Department of Biology, University of Massachusetts DartmouthNorth Dartmouth, MA, United States
| | - Mar Benavides
- Marine Biology Section, Department of Biology, University of CopenhagenHelsingør, Denmark
| | - Sophie Bonnet
- Centre National de la Recherche Scientifique, IRD, Aix-Marseille Université, Université de ToulonMarseille, France
| | - Ilana Berman-Frank
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan UniversityRamat Gan, Israel
| | - Angelicque E White
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State UniversityCorvallis, OR, United States
| | - Lasse Riemann
- Marine Biology Section, Department of Biology, University of CopenhagenHelsingør, Denmark
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23
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Sewage outburst triggers Trichodesmium bloom and enhance N 2 fixation rates. Sci Rep 2017; 7:4367. [PMID: 28663560 PMCID: PMC5491490 DOI: 10.1038/s41598-017-04622-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/25/2017] [Indexed: 11/09/2022] Open
Abstract
The southeastern Mediterranean Sea (SEMS) is a warm and sunlit marine environment with low ambient N concentration, thus considered ideal for diazotrophy by autotrophic diazotrophs such as Trichodesmium. Despite the favorable conditions, N2 fixation rates are often low and Trichodesmium has hardly been spotted in the SEMS. This study reports on the occurrence of a Trichodesmium bloom in the SEMS which was ascribed to T. erythraeum according to DNA fingerprinting of the nifH gene. We found that this bloom (1407 ± 983 cells L−1) was triggered by an intense outburst of raw sewage that supplied high concentrations of N, P and dissolved organic carbon (DOC), which resulted in low N:P (~12:1) and exceptionally high C:P (~1340:1) ratios. We surmise that these conditions provided favorable conditions for Trichodesmium bloom to form via mixotrophic metabolism. As a result, a fourfold increase in N2 fixation was recorded, which contributed ~70% to new primary production and spur a sharp increase in phytoplankton activity and biomass. The conclusions of this study point on a new paradigm for bloom-forming T. erythraeum which is tightly linked to anthropogenic sources and prompt microbial productivity in oligotrophic marine environments such as the SEMS.
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