1
|
Gao M, Andrews J, Armin G, Chakraborty S, Zehr JP, Inomura K. Rapid mode switching facilitates the growth of Trichodesmium: A model analysis. iScience 2024; 27:109906. [PMID: 38947530 PMCID: PMC11214483 DOI: 10.1016/j.isci.2024.109906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 02/28/2024] [Accepted: 05/02/2024] [Indexed: 07/02/2024] Open
Abstract
Trichodesmium is one of the dominant dinitrogen (N2) fixers in the ocean, influencing global carbon and nitrogen cycles through biochemical reactions. Although its photosynthetic activity fluctuates rapidly, the physiological or ecological advantage of this fluctuation is unclear. We develop a metabolic model of Trichodesmium that can perform daytime N2 fixation. We examined (1) the effect of the duration of switches between photosynthetic and non-photosynthetic cellular states and (2) the effect of the presence and absence of N2 fixation in photosynthetic states. Results show that a rapid switch between photosynthetic and non-photosynthetic states increases Trichodesmium growth rates by improving metabolic efficiencies due to an improved balance of C and N metabolism. This provides a strategy for previous paradoxical observations that all Trichodesmium cells can contain nitrogenase. This study reveals the importance of fluctuating photosynthetic activity and provides a mechanism for daytime N2 fixation that allows Trichodesmium to fix N2 aerobically in the global ocean.
Collapse
Affiliation(s)
- Meng Gao
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Jamal Andrews
- Biological and Environmental Sciences Graduate Program, University of Rhode Island, Kingston, RI, USA
| | - Gabrielle Armin
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Subhendu Chakraborty
- Systems Ecology Group, Leibniz Centre for Tropical Marine Research (ZMT), Bremen, Germany
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| |
Collapse
|
2
|
Zehr JP, Capone DG. Unsolved mysteries in marine nitrogen fixation. Trends Microbiol 2024; 32:532-545. [PMID: 37658011 DOI: 10.1016/j.tim.2023.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 08/03/2023] [Accepted: 08/04/2023] [Indexed: 09/03/2023]
Abstract
Biological nitrogen (N2) fixation is critical in global biogeochemical cycles and in sustaining the productivity of the oceans. There remain many unanswered questions, unresolved hypotheses, and unchallenged paradigms. The fundamental balance of N input and losses has not been fully resolved. One of the major N2-fixers, Trichodesmium, remains an enigma with intriguing biological and ecological secrets. Cyanobacterial N2 fixation, once thought to be primarily due to free-living cyanobacteria, now also appears to be dependent on microbial interactions, from microbiomes to unicellular symbioses, which remain poorly characterized. Nitrogenase genes associated with diverse non-cyanobacterial diazotrophs (NCDs) are prevalent, but their significance remains a huge knowledge gap. Answering questions, new and old, such as those discussed here, is needed to understand the ocean's N and C cycles and their responses to environmental change.
Collapse
Affiliation(s)
- Jonathan P Zehr
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA.
| | - Douglas G Capone
- Marine and Environmental Biology Section of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| |
Collapse
|
3
|
Colussi A, Bokhari SNH, Mijovilovich A, Koník P, Küpper H. Acclimation to medium-level non-lethal iron limitation: Adjustment of electron flow around the PSII and metalloprotein expression in Trichodesmium erythraeum IMS101. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149015. [PMID: 37742749 DOI: 10.1016/j.bbabio.2023.149015] [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: 03/17/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/26/2023]
Abstract
The aim of this study was to investigate how acclimation to medium-level, long-term, non-lethal iron limitation changes the electron flux around the Photosystem II of the oceanic diazotroph Trichodesmium erythraeum IMS101. Fe availability of about 5× and 100× lower than a replete level, i.e. conditions common in the natural environment of this cyanobacterium, were applied in chemostats. The response of the cells was studied not only in terms of growth, but also mechanistically, measuring the chlorophyll fluorescence of dark-adapted filaments via imaging fluorescence kinetic microscopy (FKM) with 0.3 ms time resolution. Combining these measurements with those of metal binding to proteins via online coupling of metal-free HPLC (size exclusion chromatography SEC) to sector-field ICP-MS allowed to track the fate of the photosystems, together with other metalloproteins. General increase of fluorescence has been observed, with the consequent decrease in the quantum yields φ of the PSII, while the efficiency ψ of the electron flux between PSII and the PSI remained surprisingly unchanged. This indicates the ability of Trichodesmium to cope with a situation that makes assembling the many iron clusters in Photosystem I a particular challenge, as shown by decreasing ratios of Fe to Mg in these proteins. The negative effect of Fe limitation on PSII may also be due to its fast turnover. A broader view was obtained from metalloproteomics via HPLC-ICP-MS, revealing a differential protein expression pattern under iron limitation with a drastic down-regulation especially of iron-containing proteins and some increase in low MW metal-binding complexes.
Collapse
Affiliation(s)
- Antonio Colussi
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic; University of South Bohemia, Faculty of Sciences, Department of Experimental Plant Biology, České Budějovice, Czech Republic
| | - Syed Nadeem Hussain Bokhari
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic
| | - Ana Mijovilovich
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic
| | - Peter Koník
- University of South Bohemia, Faculty of Sciences, Department of Chemistry, České Budějovice, Czech Republic
| | - Hendrik Küpper
- Czech Academy of Sciences, Biology Centre, Institute of Plant Molecular Biology, Laboratory of Plant Biophysics and Biochemistry, České Budějovice, Czech Republic; University of South Bohemia, Faculty of Sciences, Department of Experimental Plant Biology, České Budějovice, Czech Republic.
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Investigating the Unique Ability of Trichodesmium To Fix Carbon and Nitrogen Simultaneously Using MiMoSA. mSystems 2023; 8:e0060120. [PMID: 36598239 PMCID: PMC9948733 DOI: 10.1128/msystems.00601-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The open ocean is an extremely competitive environment, partially due to the dearth of nutrients. Trichodesmium erythraeum, a marine diazotrophic cyanobacterium, is a keystone species in the ocean due to its ability to fix nitrogen and leak 30 to 50% into the surrounding environment, providing a valuable source of a necessary macronutrient to other species. While there are other diazotrophic cyanobacteria that play an important role in the marine nitrogen cycle, Trichodesmium is unique in its ability to fix both carbon and nitrogen simultaneously during the day without the use of specialized cells called heterocysts to protect nitrogenase from oxygen. Here, we use the advanced modeling framework called multiscale multiobjective systems analysis (MiMoSA) to investigate how Trichodesmium erythraeum can reduce dimolecular nitrogen to ammonium in the presence of oxygen. Our simulations indicate that nitrogenase inhibition is best modeled as Michealis-Menten competitive inhibition and that cells along the filament maintain microaerobia using high flux through Mehler reactions in order to protect nitrogenase from oxygen. We also examined the effect of location on metabolic flux and found that cells at the end of filaments operate in distinctly different metabolic modes than internal cells despite both operating in a photoautotrophic mode. These results give us important insight into how this species is able to operate photosynthesis and nitrogen fixation simultaneously, giving it a distinct advantage over other diazotrophic cyanobacteria because they can harvest light directly to fuel the energy demand of nitrogen fixation. IMPORTANCE Trichodesmium erythraeum is a marine cyanobacterium responsible for approximately half of all biologically fixed nitrogen, making it an integral part of the global nitrogen cycle. Interestingly, unlike other nitrogen-fixing cyanobacteria, Trichodesmium does not use temporal or spatial separation to protect nitrogenase from oxygen poisoning; instead, it operates photosynthesis and nitrogen fixation reactions simultaneously during the day. Unfortunately, the exact mechanism the cells utilize to operate carbon and nitrogen fixation simultaneously is unknown. Here, we use an advanced metabolic modeling framework to investigate and identify the most likely mechanisms Trichodesmium uses to protect nitrogenase from oxygen. The model predicts that cells operate in a microaerobic mode, using both respiratory and Mehler reactions to dramatically reduce intracellular oxygen concentrations.
Collapse
|
6
|
Abstract
The dominant marine filamentous N2 fixer, Trichodesmium, conducts photosynthesis and N2 fixation during the daytime. Because N2 fixation is sensitive to O2, some previous studies suggested that spatial segregation of N2 fixation and photosynthesis is essential in Trichodesmium. However, this hypothesis conflicts with some observations where all the cells contain both photosystems and the N2-fixing enzyme nitrogenase. Here, we construct a systematic model simulating Trichodesmium metabolism, showing that the hypothetical spatial segregation is probably useless in increasing the Trichodesmium growth and N2 fixation, unless substances can efficiently transfer among cells with low loss to the environment. The model suggests that Trichodesmium accumulates fixed carbon in the morning and uses that in respiratory protection to reduce intracellular O2 during the mid-daytime, when photosynthesis is downregulated, allowing the occurrence of N2 fixation. A cell membrane barrier against O2 and alternative non-O2 evolving electron transfer also contribute to maintaining low intracellular O2. Our study provides a mechanism enabling N2 fixation despite the presence of photosynthesis across Trichodesmium. IMPORTANCE The filamentous Trichodesmium is a globally prominent marine nitrogen fixer. A long-standing paradox is that the nitrogen-fixing enzyme nitrogenase is sensitive to oxygen, but Trichodesmium conducts both nitrogen fixation and oxygen-evolving photosynthesis during the daytime. Previous studies using immunoassays reported that nitrogenase was limited in some specialized Trichodesmium cells (termed diazocytes), suggesting the necessity of spatial segregation of nitrogen fixation and photosynthesis. However, attempts using other methods failed to find diazocytes in Trichodesmium, causing controversy on the existence of the spatial segregation. Here, our physiological model shows that Trichodesmium can maintain low intracellular O2 in mid-daytime and achieve feasible nitrogen fixation and growth rates even without the spatial segregation, while the hypothetical spatial segregation might not be useful if substantial loss of substances to the environment occurs when they transfer among the Trichodesmium cells. Our study then suggests a possible mechanism by which Trichodesmium can survive without the spatial segregation.
Collapse
|
7
|
Cerdan-Garcia E, Baylay A, Polyviou D, Woodward EMS, Wrightson L, Mahaffey C, Lohan MC, Moore CM, Bibby TS, Robidart JC. Transcriptional responses of Trichodesmium to natural inverse gradients of Fe and P availability. THE ISME JOURNAL 2022; 16:1055-1064. [PMID: 34819612 PMCID: PMC8941076 DOI: 10.1038/s41396-021-01151-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 10/28/2021] [Accepted: 11/01/2021] [Indexed: 12/28/2022]
Abstract
The filamentous diazotrophic cyanobacterium Trichodesmium is responsible for a significant fraction of marine di-nitrogen (N2) fixation. Growth and distribution of Trichodesmium and other diazotrophs in the vast oligotrophic subtropical gyres is influenced by iron (Fe) and phosphorus (P) availability, while reciprocally influencing the biogeochemistry of these nutrients. Here we use observations across natural inverse gradients in Fe and P in the North Atlantic subtropical gyre (NASG) to demonstrate how Trichodesmium acclimates in situ to resource availability. Transcriptomic analysis identified progressive upregulation of known iron-stress biomarker genes with decreasing Fe availability, and progressive upregulation of genes involved in the acquisition of diverse P sources with decreasing P availability, while genes involved in N2 fixation were upregulated at the intersection under moderate Fe and P availability. Enhanced N2 fixation within the Fe and P co-stressed transition region was also associated with a distinct, consistent metabolic profile, including the expression of alternative photosynthetic pathways that potentially facilitate ATP generation required for N2 fixation with reduced net oxygen production. The observed response of Trichodesmium to availability of both Fe and P supports suggestions that these biogeochemically significant organisms employ unique molecular, and thus physiological responses as adaptations to specifically exploit the Fe and P co-limited niche they construct.
Collapse
Affiliation(s)
- E Cerdan-Garcia
- Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK.
| | - A Baylay
- Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK
| | - D Polyviou
- National Oceanography Centre, Southampton, SO14 3ZH, UK
| | | | - L Wrightson
- Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - C Mahaffey
- Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - M C Lohan
- Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK
| | - C M Moore
- Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK
| | - T S Bibby
- Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK
| | - J C Robidart
- National Oceanography Centre, Southampton, SO14 3ZH, UK.
| |
Collapse
|
8
|
Held NA, Waterbury JB, Webb EA, Kellogg RM, McIlvin MR, Jakuba M, Valois FW, Moran DM, Sutherland KM, Saito MA. Dynamic diel proteome and daytime nitrogenase activity supports buoyancy in the cyanobacterium Trichodesmium. Nat Microbiol 2022; 7:300-311. [PMID: 35013592 PMCID: PMC10288448 DOI: 10.1038/s41564-021-01028-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 11/17/2021] [Indexed: 12/13/2022]
Abstract
Cyanobacteria of the genus Trichodesmium provide about 80 Tg of fixed nitrogen to the surface ocean per year and contribute to marine biogeochemistry, including the sequestration of carbon dioxide. Trichodesmium fixes nitrogen in the daylight, despite the incompatibility of the nitrogenase enzyme with oxygen produced during photosynthesis. While the mechanisms protecting nitrogenase remain unclear, all proposed strategies require considerable resource investment. Here we identify a crucial benefit of daytime nitrogen fixation in Trichodesmium spp. that may counteract these costs. We analysed diel proteomes of cultured and field populations of Trichodesmium in comparison with the marine diazotroph Crocosphaera watsonii WH8501, which fixes nitrogen at night. Trichodesmium's proteome is extraordinarily dynamic and demonstrates simultaneous photosynthesis and nitrogen fixation, resulting in balanced particulate organic carbon and particulate organic nitrogen production. Unlike Crocosphaera, which produces large quantities of glycogen as an energy store for nitrogenase, proteomic evidence is consistent with the idea that Trichodesmium reduces the need to produce glycogen by supplying energy directly to nitrogenase via soluble ferredoxin charged by the photosynthesis protein PsaC. This minimizes ballast associated with glycogen, reducing cell density and decreasing sinking velocity, thus supporting Trichodesmium's niche as a buoyant, high-light-adapted colony forming cyanobacterium. To occupy its niche of simultaneous nitrogen fixation and photosynthesis, Trichodesmium appears to be a conspicuous consumer of iron, and has therefore developed unique iron-acquisition strategies, including the use of iron-rich dust. Particle capture by buoyant Trichodesmium colonies may increase the residence time and degradation of mineral iron in the euphotic zone. These findings describe how cellular biochemistry defines and reinforces the ecological and biogeochemical function of these keystone marine diazotrophs.
Collapse
Affiliation(s)
- Noelle A Held
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
- Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Environmental Systems Science, ETH, Zurich, Switzerland
| | - John B Waterbury
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Eric A Webb
- Marine and Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Riss M Kellogg
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
- Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Matthew R McIlvin
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Michael Jakuba
- Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Frederica W Valois
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Dawn M Moran
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Kevin M Sutherland
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
- Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
| | - Mak A Saito
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
| |
Collapse
|
9
|
Inomura K, Deutsch C, Masuda T, Prášil O, Follows MJ. Quantitative models of nitrogen-fixing organisms. Comput Struct Biotechnol J 2020; 18:3905-3924. [PMID: 33335688 PMCID: PMC7733014 DOI: 10.1016/j.csbj.2020.11.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 10/26/2022] Open
Abstract
Nitrogen-fixing organisms are of importance to the environment, providing bioavailable nitrogen to the biosphere. Quantitative models have been used to complement the laboratory experiments and in situ measurements, where such evaluations are difficult or costly. Here, we review the current state of the quantitative modeling of nitrogen-fixing organisms and ways to enhance the bridge between theoretical and empirical studies.
Collapse
Affiliation(s)
- Keisuke Inomura
- School of Oceanography, University of Washington, Seattle, WA, USA
| | - Curtis Deutsch
- School of Oceanography, University of Washington, Seattle, WA, USA
| | - Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, Třeboň, Czech Republic
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, Třeboň, Czech Republic
| | - Michael J. Follows
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| |
Collapse
|
10
|
Heterogeneous nitrogen fixation rates confer energetic advantage and expanded ecological niche of unicellular diazotroph populations. Commun Biol 2020; 3:172. [PMID: 32286494 PMCID: PMC7156374 DOI: 10.1038/s42003-020-0894-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/13/2020] [Indexed: 11/23/2022] Open
Abstract
Nitrogen fixing plankton provide nitrogen to fuel marine ecosystems and biogeochemical cycles but the factors that constrain their growth and habitat remain poorly understood. Here we investigate the importance of metabolic specialization in unicellular diazotroph populations, using laboratory experiments and model simulations. In clonal cultures of Crocosphaera watsonii and Cyanothece sp. spiked with 15N2, cellular 15N enrichment developed a bimodal distribution within colonies, indicating that N2 fixation was confined to a subpopulation. In a model of population metabolism, heterogeneous nitrogen (N2) fixation rates substantially reduce the respiration rate required to protect nitrogenase from O2. The energy savings from metabolic specialization is highest at slow growth rates, allowing populations to survive in deeper waters where light is low but nutrients are high. Our results suggest that heterogeneous N2 fixation in colonies of unicellular diazotrophs confers an energetic advantage that expands the ecological niche and may have facilitated the evolution of multicellular diazotrophs. Takako Masuda et al. show that individual cells in clonal populations of Crocosphaera watsonii and Cyanothece sp exhibit varied nitrogen fixation rates. This heterogeneity within the population decreases the energetic cost of respiration and expands the viable habitats for these unicellular diazotrophs.
Collapse
|
11
|
Mechanistic Model for the Coexistence of Nitrogen Fixation and Photosynthesis in Marine Trichodesmium. mSystems 2019; 4:4/4/e00210-19. [PMID: 31387928 PMCID: PMC6687940 DOI: 10.1128/msystems.00210-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Trichodesmium is a major nitrogen-fixing cyanobacterium and exerts a significant influence on the oceanic nitrogen cycle. It is also a widely used model organism in laboratory studies. Since the nitrogen-fixing enzyme nitrogenase is extremely sensitive to oxygen, how these surface-dwelling plankton manage the two conflicting processes of nitrogen fixation and photosynthesis has been a long-standing question. In this study, we developed a simple model of metabolic fluxes of Trichodesmium capturing observed daily cycles of photosynthesis, nitrogen fixation, and boundary layer oxygen concentrations. The model suggests that forming a chain of cells for spatially segregating nitrogen fixation and photosynthesis is essential but not sufficient. It also requires a barrier against oxygen diffusion and high rates of oxygen scavenging by respiration. Finally, the model indicates that the life span of intracellular oxygen is extremely short, thus enabling cells to instantly create a low-oxygen environment upon deactivation of photosynthesis. The cyanobacterium Trichodesmium is an important contributor of new nitrogen (N) to the surface ocean, but its strategies for protecting the nitrogenase enzyme from inhibition by oxygen (O2) remain poorly understood. We present a dynamic physiological model to evaluate hypothesized conditions that would allow Trichodesmium to carry out its two conflicting metabolic processes of N2 fixation and photosynthesis. First, the model indicates that managing cellular O2 to permit N2 fixation requires high rates of respiratory O2 consumption. The energetic cost amounts to ∼80% of daily C fixation, comparable to the observed diminution of the growth rate of Trichodesmium relative to other phytoplankton. Second, by forming a trichome of connected cells, Trichodesmium can segregate N2 fixation from photosynthesis. The transfer of stored C to N-fixing cells fuels the respiratory O2 consumption that protects nitrogenase, while the reciprocal transfer of newly fixed N to C-fixing cells supports cellular growth. Third, despite Trichodesmium lacking the structural barrier found in heterocystous species, the model predicts low diffusivity of cell membranes, a function that may be explained by the presence of Gram-negative membrane, production of extracellular polysaccharide substances (EPS), and “buffer cells” that intervene between N2-fixing and photosynthetic cells. Our results suggest that all three factors—respiratory protection, trichome formation, and diffusion barriers—represent essential strategies that, despite their energetic costs, facilitate the growth of Trichodesmium in the oligotrophic aerobic ocean and permit it to be a major source of new reactive nitrogen. IMPORTANCETrichodesmium is a major nitrogen-fixing cyanobacterium and exerts a significant influence on the oceanic nitrogen cycle. It is also a widely used model organism in laboratory studies. Since the nitrogen-fixing enzyme nitrogenase is extremely sensitive to oxygen, how these surface-dwelling plankton manage the two conflicting processes of nitrogen fixation and photosynthesis has been a long-standing question. In this study, we developed a simple model of metabolic fluxes of Trichodesmium capturing observed daily cycles of photosynthesis, nitrogen fixation, and boundary layer oxygen concentrations. The model suggests that forming a chain of cells for spatially segregating nitrogen fixation and photosynthesis is essential but not sufficient. It also requires a barrier against oxygen diffusion and high rates of oxygen scavenging by respiration. Finally, the model indicates that the life span of intracellular oxygen is extremely short, thus enabling cells to instantly create a low-oxygen environment upon deactivation of photosynthesis.
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Boatman TG, Davey PA, Lawson T, Geider RJ. The physiological cost of diazotrophy for Trichodesmium erythraeum IMS101. PLoS One 2018; 13:e0195638. [PMID: 29641568 PMCID: PMC5895029 DOI: 10.1371/journal.pone.0195638] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 03/26/2018] [Indexed: 11/24/2022] Open
Abstract
Trichodesmium plays a significant role in the oligotrophic oceans, fixing nitrogen in an area corresponding to half of the Earth's surface, representing up to 50% of new production in some oligotrophic tropical and subtropical oceans. Whilst Trichodesmium blooms at the surface exhibit a strong dependence on diazotrophy, colonies at depth or at the surface after a mixing event could be utilising additional N-sources. We conducted experiments to establish how acclimation to varying N-sources affects the growth, elemental composition, light absorption coefficient, N2 fixation, PSII electron transport rate and the relationship between net and gross photosynthetic O2 exchange in T. erythraeum IMS101. To do this, cultures were acclimated to growth medium containing NH4+ and NO3- (replete concentrations) or N2 only (diazotrophic control). The light dependencies of O2 evolution and O2 uptake were measured using membrane inlet mass spectrometry (MIMS), while PSII electron transport rates were measured from fluorescence light curves (FLCs). We found that at a saturating light intensity, Trichodesmium growth was ~ 10% and 13% lower when grown on N2 than with NH4+ and NO3-, respectively. Oxygen uptake increased linearly with net photosynthesis across all light intensities ranging from darkness to 1100 μmol photons m-2 s-1. The maximum rates and initial slopes of light response curves for C-specific gross and net photosynthesis and the slope of the relationship between gross and net photosynthesis increased significantly under non-diazotrophic conditions. We attribute these observations to a reduced expenditure of reductant and ATP for nitrogenase activity under non-diazotrophic conditions which allows NADPH and ATP to be re-directed to CO2 fixation and/or biosynthesis. The energy and reductant conserved through utilising additional N-sources could enhance Trichodesmium's productivity and growth and have major implications for its role in ocean C and N cycles.
Collapse
Affiliation(s)
- Tobias G. Boatman
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Phillip A. Davey
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Tracy Lawson
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Richard J. Geider
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| |
Collapse
|
14
|
Eichner MJ, Klawonn I, Wilson ST, Littmann S, Whitehouse MJ, Church MJ, Kuypers MM, Karl DM, Ploug H. Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO 2. ISME JOURNAL 2017; 11:1305-1317. [PMID: 28398346 PMCID: PMC5437350 DOI: 10.1038/ismej.2017.15] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/19/2016] [Accepted: 01/09/2017] [Indexed: 11/20/2022]
Abstract
Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2 were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2 concentrations over a day–night cycle. O2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2 (up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l−1 proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2 levels, whereas N2 fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.
Collapse
Affiliation(s)
- Meri J Eichner
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Isabell Klawonn
- Department of Ecology, Environment and Plant Sciences, University of Stockholm, Stockholm, Sweden
| | - Samuel T Wilson
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Sten Littmann
- Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Martin J Whitehouse
- Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
| | - Matthew J Church
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Marcel Mm Kuypers
- Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - David M Karl
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Helle Ploug
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| |
Collapse
|
15
|
Gardner JJ, Boyle NR. The use of genome-scale metabolic network reconstruction to predict fluxes and equilibrium composition of N-fixing versus C-fixing cells in a diazotrophic cyanobacterium, Trichodesmium erythraeum. BMC SYSTEMS BIOLOGY 2017; 11:4. [PMID: 28103880 PMCID: PMC5244712 DOI: 10.1186/s12918-016-0383-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 12/21/2016] [Indexed: 01/08/2023]
Abstract
Background Computational, genome based predictions of organism phenotypes has enhanced the ability to investigate the biological phenomena that help organisms survive and respond to their environments. In this study, we have created the first genome-scale metabolic network reconstruction of the nitrogen fixing cyanobacterium T. erythraeum and used genome-scale modeling approaches to investigate carbon and nitrogen fluxes as well as growth and equilibrium population composition. Results We created a genome-scale reconstruction of T. erythraeum with 971 reactions, 986 metabolites, and 647 unique genes. We then used data from previous studies as well as our own laboratory data to establish a biomass equation and two distinct submodels that correspond to the two cell types formed by T. erythraeum. We then use flux balance analysis and flux variability analysis to generate predictions for how metabolism is distributed to account for the unique productivity of T. erythraeum. Finally, we used in situ data to constrain the model, infer time dependent population compositions and metabolite production using dynamic Flux Balance Analysis. We find that our model predicts equilibrium compositions similar to laboratory measurements, approximately 15.5% diazotrophs for our model versus 10-20% diazotrophs reported in literature. We also found that equilibrium was the most efficient mode of growth and that equilibrium was stoichiometrically mediated. Moreover, the model predicts that nitrogen leakage is an essential condition of optimality for T. erythraeum; cells leak approximately 29.4% total fixed nitrogen when growing at the optimal growth rate, which agrees with values observed in situ. Conclusion The genome-metabolic network reconstruction allows us to use constraints based modeling approaches to predict growth and optimal cellular composition in T. erythraeum colonies. Our predictions match both in situ and laboratory data, indicating that stoichiometry of metabolic reactions plays a large role in the differentiation and composition of different cell types. In order to realize the full potential of the model, advance modeling techniques which account for interactions between colonies, the environment and surrounding species need to be developed. Electronic supplementary material The online version of this article (doi:10.1186/s12918-016-0383-z) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Joseph J Gardner
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, 80401, USA
| | - Nanette R Boyle
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO, 80401, USA.
| |
Collapse
|
16
|
Snow JT, Polyviou D, Skipp P, Chrismas NAM, Hitchcock A, Geider R, Moore CM, Bibby TS. Quantifying Integrated Proteomic Responses to Iron Stress in the Globally Important Marine Diazotroph Trichodesmium. PLoS One 2015; 10:e0142626. [PMID: 26562022 PMCID: PMC4642986 DOI: 10.1371/journal.pone.0142626] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 10/23/2015] [Indexed: 02/03/2023] Open
Abstract
Trichodesmium is a biogeochemically important marine cyanobacterium, responsible for a significant proportion of the annual 'new' nitrogen introduced into the global ocean. These non-heterocystous filamentous diazotrophs employ a potentially unique strategy of near-concurrent nitrogen fixation and oxygenic photosynthesis, potentially burdening Trichodesmium with a particularly high iron requirement due to the iron-binding proteins involved in these processes. Iron availability may therefore have a significant influence on the biogeography of Trichodesmium. Previous investigations of molecular responses to iron stress in this keystone marine microbe have largely been targeted. Here a holistic approach was taken using a label-free quantitative proteomics technique (MSE) to reveal a sophisticated multi-faceted proteomic response of Trichodesmium erythraeum IMS101 to iron stress. Increased abundances of proteins known to be involved in acclimation to iron stress and proteins known or predicted to be involved in iron uptake were observed, alongside decreases in the abundances of iron-binding proteins involved in photosynthesis and nitrogen fixation. Preferential loss of proteins with a high iron content contributed to overall reductions of 55-60% in estimated proteomic iron requirements. Changes in the abundances of iron-binding proteins also suggested the potential importance of alternate photosynthetic pathways as Trichodesmium reallocates the limiting resource under iron stress. Trichodesmium therefore displays a significant and integrated proteomic response to iron availability that likely contributes to the ecological success of this species in the ocean.
Collapse
Affiliation(s)
- Joseph T. Snow
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom
- Stem Cell and Leukaemia Proteomics Laboratory, Manchester Academic Health Science Centre, The University of Manchester, Wolfson Molecular Imaging Centre, Manchester, United Kingdom
- * E-mail:
| | - Despo Polyviou
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom
| | - Paul Skipp
- Centre for Proteomic Research, University of Southampton, Southampton, United Kingdom
| | - Nathan A. M. Chrismas
- School of Geographical Sciences, University of Bristol, University Road, Clifton, Bristol, United Kingdom
| | - Andrew Hitchcock
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, United Kingdom
| | - Richard Geider
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - C. Mark Moore
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom
| | - Thomas S. Bibby
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, United Kingdom
| |
Collapse
|
17
|
Karaushu EV, Lazebnaya IV, Kravzova TR, Vorobey NA, Lazebny OE, Kiriziy DA, Olkhovich OP, Taran NY, Kots SY, Popova AA, Omarova E, Koksharova OA. Biochemical and Molecular Phylogenetic Study of Agriculturally Useful Association of a Nitrogen-Fixing Cyanobacterium and Nodule Sinorhizobium with Medicago sativa L. BIOMED RESEARCH INTERNATIONAL 2015; 2015:202597. [PMID: 26114100 PMCID: PMC4465650 DOI: 10.1155/2015/202597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 02/24/2015] [Indexed: 11/17/2022]
Abstract
Seed inoculation with bacterial consortium was found to increase legume yield, providing a higher growth than the standard nitrogen treatment methods. Alfalfa plants were inoculated by mono- and binary compositions of nitrogen-fixing microorganisms. Their physiological and biochemical properties were estimated. Inoculation by microbial consortium of Sinorhizobium meliloti T17 together with a new cyanobacterial isolate Nostoc PTV was more efficient than the single-rhizobium strain inoculation. This treatment provides an intensification of the processes of biological nitrogen fixation by rhizobia bacteria in the root nodules and an intensification of plant photosynthesis. Inoculation by bacterial consortium stimulates growth of plant mass and rhizogenesis and leads to increased productivity of alfalfa and to improving the amino acid composition of plant leaves. The full nucleotide sequence of the rRNA gene cluster and partial sequence of the dinitrogenase reductase (nifH) gene of Nostoc PTV were deposited to GenBank (JQ259185.1, JQ259186.1). Comparison of these gene sequences of Nostoc PTV with all sequences present at the GenBank shows that this cyanobacterial strain does not have 100% identity with any organisms investigated previously. Phylogenetic analysis showed that this cyanobacterium clustered with high credibility values with Nostoc muscorum.
Collapse
Affiliation(s)
- E. V. Karaushu
- Educational and Scientific “Institute of Biology”, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv 01601, Ukraine
| | - I. V. Lazebnaya
- N. I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Gubkin Street 3, Moscow 119333, Russia
| | - T. R. Kravzova
- Lomonosov Moscow State University, Biocenter, Leninskie Gory 1-12, Moscow 119991, Russia
| | - N. A. Vorobey
- Institute of Plant Physiology and Genetics, National Academy of Sciences of Ukraine, 31/17 Vasylkivska Street, Kyiv 03022, Ukraine
| | - O. E. Lazebny
- N. K. Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova Street 26, Moscow 119334, Russia
| | - D. A. Kiriziy
- Institute of Plant Physiology and Genetics, National Academy of Sciences of Ukraine, 31/17 Vasylkivska Street, Kyiv 03022, Ukraine
| | - O. P. Olkhovich
- Educational and Scientific “Institute of Biology”, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv 01601, Ukraine
| | - N. Yu. Taran
- Educational and Scientific “Institute of Biology”, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv 01601, Ukraine
| | - S. Ya. Kots
- Institute of Plant Physiology and Genetics, National Academy of Sciences of Ukraine, 31/17 Vasylkivska Street, Kyiv 03022, Ukraine
| | - A. A. Popova
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia
| | - E. Omarova
- Lomonosov Moscow State University, Belozersky Institute of Physical-Chemical Biology, Leninskie Gory 1-40, Moscow 119992, Russia
| | - O. A. Koksharova
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia
- Lomonosov Moscow State University, Belozersky Institute of Physical-Chemical Biology, Leninskie Gory 1-40, Moscow 119992, Russia
| |
Collapse
|
18
|
Cai X, Gao K, Fu F, Campbell DA, Beardall J, Hutchins DA. Electron transport kinetics in the diazotrophic cyanobacterium Trichodesmium spp. grown across a range of light levels. PHOTOSYNTHESIS RESEARCH 2015; 124:45-56. [PMID: 25616859 DOI: 10.1007/s11120-015-0081-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 01/06/2015] [Indexed: 05/13/2023]
Abstract
The diazotrophic cyanobacterium Trichodesmium is a major contributor to marine nitrogen fixation. We analyzed how light acclimation influences the photophysiological performance of Trichodesmium IMS101 during exponential growth in semi-continuous nitrogen fixing cultures under light levels of 70, 150, 250, and 400 μmol photons m(-2) s(-1), across diel cycles. There were close correlations between growth rate, trichome length, particulate organic carbon and nitrogen assimilation, and cellular absorbance, which all peaked at 150 μmol photons m(-2) s(-1). Growth rate was light saturated by about 100 μmol photons m(-2) s(-1) and was photoinhibited above 150 μmol photons m(-2) s(-1). In contrast, the light level (I k) to saturate PSII electron transport (e (-) PSII(-1) s(-1)) was much higher, in the range of 450-550 μmol photons m(-2) s(-1), and increased with growth light. Growth rate correlates with the absorption cross section as well as with absorbed photons per cell, but not to electron transport per PSII; this disparity suggests that numbers of PSII in a cell, along with the energy allocation between two photosystems and the state transition mechanism underlie the changes in growth rates. The rate of state transitions after a transfer to darkness increased with growth light, indicating faster respiratory input into the intersystem electron transport chain.
Collapse
Affiliation(s)
- Xiaoni Cai
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian, China
| | | | | | | | | | | |
Collapse
|
19
|
Eichner M, Kranz SA, Rost B. Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium. PHYSIOLOGIA PLANTARUM 2014; 152:316-30. [PMID: 24547877 PMCID: PMC4260171 DOI: 10.1111/ppl.12172] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 01/17/2014] [Accepted: 01/21/2014] [Indexed: 05/03/2023]
Abstract
To predict effects of climate change and possible feedbacks, it is crucial to understand the mechanisms behind CO2 responses of biogeochemically relevant phytoplankton species. Previous experiments on the abundant N2 fixers Trichodesmium demonstrated strong CO2 responses, which were attributed to an energy reallocation between its carbon (C) and nitrogen (N) acquisition. Pursuing this hypothesis, we manipulated the cellular energy budget by growing Trichodesmium erythraeum IMS101 under different CO2 partial pressure (pCO2 ) levels (180, 380, 980 and 1400 µatm) and N sources (N2 and NO3 (-) ). Subsequently, biomass production and the main energy-generating processes (photosynthesis and respiration) and energy-consuming processes (N2 fixation and C acquisition) were measured. While oxygen fluxes and chlorophyll fluorescence indicated that energy generation and its diurnal cycle was neither affected by pCO2 nor N source, cells differed in production rates and composition. Elevated pCO2 increased N2 fixation and organic C and N contents. The degree of stimulation was higher for nitrogenase activity than for cell contents, indicating a pCO2 effect on the transfer efficiency from N2 to biomass. pCO2 -dependent changes in the diurnal cycle of N2 fixation correlated well with C affinities, confirming the interactions between N and C acquisition. Regarding effects of the N source, production rates were enhanced in NO3 (-) grown cells, which we attribute to the higher N retention and lower ATP demand compared with N2 fixation. pCO2 effects on C affinity were less pronounced in NO3 (-) users than N2 fixers. Our study illustrates the necessity to understand energy budgets and fluxes under different environmental conditions for explaining indirect effects of rising pCO2 .
Collapse
Affiliation(s)
- Meri Eichner
- Marine Biogeosciences, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und MeeresforschungBremerhaven, 27570, Germany
| | - Sven A Kranz
- Department of Geosciences, Princeton UniversityPrinceton, NJ, 08544, USA
| | - Björn Rost
- Marine Biogeosciences, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und MeeresforschungBremerhaven, 27570, Germany
| |
Collapse
|
20
|
Nuester J, Newville M, Twining BS. Distributions of iron, phosphorus and sulfur along trichomes of the cyanobacteria Trichodesmium. Metallomics 2014; 6:1141-9. [DOI: 10.1039/c4mt00042k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Changes in the elemental composition within trichomes of the nonheterocystous cyanobacteriaTrichodesmiumare potentially related to N2-fixation.
Collapse
Affiliation(s)
| | - Matthew Newville
- Center for Advanced Radiation Sources
- The University of Chicago
- Argonne, USA
| | | |
Collapse
|
21
|
Mechanisms Modulating Energy Arriving at Reaction Centers in Cyanobacteria. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2014. [DOI: 10.1007/978-94-017-9032-1_22] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
22
|
Thompson AW, Zehr JP. Cellular interactions: lessons from the nitrogen-fixing cyanobacteria. JOURNAL OF PHYCOLOGY 2013; 49:1024-1035. [PMID: 27007623 DOI: 10.1111/jpy.12117] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Accepted: 08/17/2013] [Indexed: 06/05/2023]
Abstract
Marine nitrogen-fixing cyanobacteria play a central role in the open-ocean microbial community by providing fixed nitrogen (N) to the ocean from atmospheric dinitrogen (N2 ) gas. Once thought to be dominated by one genus of cyanobacteria, Trichodesmium, it is now clear that marine N2 -fixing cyanobacteria in the open ocean are more diverse, include several previously unknown symbionts, and are geographically more widespread than expected. The next challenge is to understand the ecological implications of this genetic and phenotypic diversity for global oceanic N cycling. One intriguing aspect of the cyanobacterial N2 fixers ecology is the range of cellular interactions they engage in, either with cells of their own species or with photosynthetic protists. From organelle-like integration with the host cell to a free-living existence, N2 -fixing cyanobacteria represent the range of types of interactions that occur among microbes in the open ocean. Here, we review what is known about the cellular interactions carried out by marine N2 -fixing cyanobacteria and where future work can help. Discoveries related to the functional roles of these specialized cells in food webs and the microbial community will improve how we interpret their distribution and abundance patterns and contributions to global N and carbon (C) cycles.
Collapse
Affiliation(s)
- Anne W Thompson
- Department of Ocean Sciences, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
| |
Collapse
|
23
|
Ferimazova N, Felcmanová K, Setlíková E, Küpper H, Maldener I, Hauska G, Sedivá B, Prášil O. Regulation of photosynthesis during heterocyst differentiation in Anabaena sp. strain PCC 7120 investigated in vivo at single-cell level by chlorophyll fluorescence kinetic microscopy. PHOTOSYNTHESIS RESEARCH 2013; 116:79-91. [PMID: 23918299 DOI: 10.1007/s11120-013-9897-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/21/2013] [Indexed: 06/02/2023]
Abstract
Changes of photosynthetic activity in vivo of individual heterocysts and vegetative cells in the diazotrophic cyanobacterium Anabaena sp. strain PCC 7120 during the course of diazotrophic acclimation were determined using fluorescence kinetic microscopy (FKM). Distinct phases of stress and acclimation following nitrogen step-down were observed. The first was a period of perception, in which the cells used their internally stored nitrogen without detectable loss of PS II activity or pigments. In the second, the stress phase of nitrogen limitation, the cell differentiation occurred and an abrupt decline of fluorescence yield was observed. This decline in fluorescence was not paralleled by a corresponding decline in photosynthetic pigment content and PS II activity. Both maximal quantum yield and sustained electron flow were not altered in vegetative cells, only in the forming heterocysts. The third, acclimation phase started first in the differentiating heterocysts with a recovery of PS II photochemical yields [Formula: see text] Afterwards, the onset of nitrogenase activity was observed, followed by the restoration of antenna pigments in the vegetative cells, but not in the heterocysts. Surprisingly, mature heterocysts were found to have an intact PS II as judged by photochemical yields, but a strongly reduced PS II-associated antenna as judged by decreased F 0. The possible importance of the functional PS II in heterocysts is discussed. Also, the FKM approach allowed to follow in vivo and evaluate the heterogeneity in photosynthetic performance among individual vegetative cells as well as heterocysts in the course of diazotrophic acclimation. Some cells along the filament (so-called "superbright cells") were observed to display transiently increased fluorescence yield, which apparently proceeded by apoptosis.
Collapse
Affiliation(s)
- Naila Ferimazova
- Laboratory of Photosynthesis-Algatech, Institute of Microbiology, Academy of Sciences of the Czech Republic, Třeboň, 379 81, Czech Republic
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Bergman B, Sandh G, Lin S, Larsson J, Carpenter EJ. Trichodesmium--a widespread marine cyanobacterium with unusual nitrogen fixation properties. FEMS Microbiol Rev 2012; 37:286-302. [PMID: 22928644 PMCID: PMC3655545 DOI: 10.1111/j.1574-6976.2012.00352.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 08/13/2012] [Accepted: 08/21/2012] [Indexed: 12/03/2022] Open
Abstract
The last several decades have witnessed dramatic advances in unfolding the diversity and commonality of oceanic diazotrophs and their N2-fixing potential. More recently, substantial progress in diazotrophic cell biology has provided a wealth of information on processes and mechanisms involved. The substantial contribution by the diazotrophic cyanobacterial genus Trichodesmium to the nitrogen influx of the global marine ecosystem is by now undisputable and of paramount ecological importance, while the underlying cellular and molecular regulatory physiology has only recently started to unfold. Here, we explore and summarize current knowledge, related to the optimization of its diazotrophic capacity, from genomics to ecophysiological processes, via, for example, cellular differentiation (diazocytes) and temporal regulations, and suggest cellular research avenues that now ought to be explored.
Collapse
|
25
|
Tamary E, Kiss V, Nevo R, Adam Z, Bernát G, Rexroth S, Rögner M, Reich Z. Structural and functional alterations of cyanobacterial phycobilisomes induced by high-light stress. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:319-27. [PMID: 22138629 DOI: 10.1016/j.bbabio.2011.11.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 11/06/2011] [Accepted: 11/09/2011] [Indexed: 11/18/2022]
Abstract
Exposure of cyanobacterial or red algal cells to high light has been proposed to lead to excitonic decoupling of the phycobilisome antennae (PBSs) from the reaction centers. Here we show that excitonic decoupling of PBSs of Synechocystis sp. PCC 6803 is induced by strong light at wavelengths that excite either phycobilin or chlorophyll pigments. We further show that decoupling is generally followed by disassembly of the antenna complexes and/or their detachment from the thylakoid membrane. Based on a previously proposed mechanism, we suggest that local heat transients generated in the PBSs by non-radiative energy dissipation lead to alterations in thermo-labile elements, likely in certain rod and core linker polypeptides. These alterations disrupt the transfer of excitation energy within and from the PBSs and destabilize the antenna complexes and/or promote their dissociation from the reaction centers and from the thylakoid membranes. Possible implications of the aforementioned alterations to adaptation of cyanobacteria to light and other environmental stresses are discussed.
Collapse
Affiliation(s)
- Eyal Tamary
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Sandh G, Xu L, Bergman B. Diazocyte development in the marine diazotrophic cyanobacterium Trichodesmium. MICROBIOLOGY-SGM 2011; 158:345-352. [PMID: 22053003 DOI: 10.1099/mic.0.051268-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The establishment of non-diazotrophic cultures of the filamentous marine cyanobacterium Trichodesmium erythraeum IMS101 enabled the first detailed investigation of the process leading to the development of its unique nitrogen-fixing cell type, the diazocyte. Trichome heterogeneity was apparent already within 3-8 h, while the differentiation of mature diazocytes, containing the nitrogenase enzyme, required 27 h after the removal of combined nitrogen. The distribution of 'pro-diazocytes' within the trichomes correlates with the localization of mature diazocytes, which suggests that pattern regulation is an early event during diazocyte development. The development was initially identified as changes in the subcellular ultrastructure, most notably the degradation of glycogen granules and gas vacuoles. These changes were preceded by the induced expression of the global nitrogen regulator ntcA at an early stage of combined nitrogen deprivation, followed by elevated expression of genes related to nitrogen metabolism and their corresponding proteins. The strongest induction (10-fold) was related to the transcription of the respiratory gene coxB2, apparent already at an early stage, which suggests an important role for respiration and the subsequent energy generation in the subcellular changes found, and in the creation of the reducing environment required for nitrogen fixation in diazocytes.
Collapse
Affiliation(s)
- Gustaf Sandh
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
| | - Linghua Xu
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
| | - Birgitta Bergman
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
| |
Collapse
|
27
|
Kranz SA, Eichner M, Rost B. Interactions between CCM and N2 fixation in Trichodesmium. PHOTOSYNTHESIS RESEARCH 2011; 109:73-84. [PMID: 21190135 DOI: 10.1007/s11120-010-9611-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 12/17/2010] [Indexed: 05/30/2023]
Abstract
In view of the current increase in atmospheric pCO(2) and concomitant changes in the marine environment, it is crucial to assess, understand, and predict future responses of ecologically relevant phytoplankton species. The diazotrophic cyanobacterium Trichodesmium erythraeum was found to respond strongly to elevated pCO(2) by increasing growth, production rates, and N(2) fixation. The magnitude of these CO(2) effects exceeds those previously seen in other phytoplankton, raising the question about the underlying mechanisms. Here, we review recent publications on metabolic pathways of Trichodesmium from a gene transcription level to the protein activities and energy fluxes. Diurnal patterns of nitrogenase activity change markedly with CO(2) availability, causing higher diel N(2) fixation rates under elevated pCO(2). The observed responses to elevated pCO(2) could not be attributed to enhanced energy generation via gross photosynthesis, although there are indications for CO(2)-dependent changes in ATP/NADPH + H(+) production. The CO(2) concentrating mechanism (CCM) in Trichodesmium is primarily based on HCO(3)(-) uptake. Although only little CO(2) uptake was detected, the NDH complex seems to play a crucial role in internal cycling of inorganic carbon, especially under elevated pCO(2). Affinities for inorganic carbon change over the day, closely following the pattern in N(2) fixation, and generally decrease with increasing pCO(2). This down-regulation of CCM activity and the simultaneously enhanced N(2) fixation point to a shift in energy allocation from carbon acquisition to N(2) fixation under elevated pCO(2) levels. A strong light modulation of CO(2) effects further corroborates the role of energy fluxes as a key to understand the responses of Trichodesmium.
Collapse
Affiliation(s)
- Sven A Kranz
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
| | | | | |
Collapse
|
28
|
Sandh G, Ran L, Xu L, Sundqvist G, Bulone V, Bergman B. Comparative proteomic profiles of the marine cyanobacterium Trichodesmium erythraeum
IMS101 under different nitrogen regimes. Proteomics 2011; 11:406-19. [DOI: 10.1002/pmic.201000382] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 10/04/2010] [Accepted: 11/08/2010] [Indexed: 11/06/2022]
|
29
|
Levitan O, Sudhaus S, LaRoche J, Berman-Frank I. The influence of pCO2 and temperature on gene expression of carbon and nitrogen pathways in Trichodesmium IMS101. PLoS One 2010; 5:e15104. [PMID: 21151907 PMCID: PMC2997788 DOI: 10.1371/journal.pone.0015104] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 10/21/2010] [Indexed: 11/28/2022] Open
Abstract
Growth, protein amount, and activity levels of metabolic pathways in Trichodesmium are influenced by environmental changes such as elevated pCO(2) and temperature. This study examines changes in the expression of essential metabolic genes in Trichodesmium grown under a matrix of pCO(2) (400 and 900 µatm) and temperature (25 and 31°C). Using RT-qPCR, we studied 21 genes related to four metabolic functional groups: CO(2) concentrating mechanism (bicA1, bicA2, ccmM, ccmK2, ccmK3, ndhF4, ndhD4, ndhL, chpX), energy metabolism (atpB, sod, prx, glcD), nitrogen metabolism (glnA, hetR, nifH), and inorganic carbon fixation and photosynthesis (rbcL, rca, psaB, psaC, psbA). nifH and most photosynthetic genes exhibited relatively high abundance and their expression was influenced by both environmental parameters. A two to three orders of magnitude increase was observed for glnA and hetR only when both pCO(2) and temperature were elevated. CO(2) concentrating mechanism genes were not affected by pCO(2) and temperature and their expression levels were markedly lower than that of the nitrogen metabolism and photosynthetic genes. Many of the CO(2) concentrating mechanism genes were co-expressed throughout the day. Our results demonstrate that in Trichodesmium, CO(2) concentrating mechanism genes are constitutively expressed. Co-expression of genes from different functional groups were frequently observed during the first half of the photoperiod when oxygenic photosynthesis and N(2) fixation take place, pointing at the tight and complex regulation of gene expression in Trichodesmium. Here we provide new data linking environmental changes of pCO(2) and temperature to gene expression in Trichodesmium. Although gene expression indicates an active metabolic pathway, there is often an uncoupling between transcription and enzyme activity, such that transcript level cannot usually be directly extrapolated to metabolic activity.
Collapse
Affiliation(s)
- Orly Levitan
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel.
| | | | | | | |
Collapse
|
30
|
The Ecology of Nitrogen Fixation in Cyanobacterial Mats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 675:31-45. [DOI: 10.1007/978-1-4419-1528-3_3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
|
31
|
Levitan O, Brown CM, Sudhaus S, Campbell D, LaRoche J, Berman-Frank I. Regulation of nitrogen metabolism in the marine diazotroph Trichodesmium IMS101 under varying temperatures and atmospheric CO2 concentrations. Environ Microbiol 2010; 12:1899-912. [DOI: 10.1111/j.1462-2920.2010.02195.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
32
|
Andresen E, Lohscheider J, Setlikova E, Adamska I, Simek M, Küpper H. Acclimation of Trichodesmium erythraeum ISM101 to high and low irradiance analysed on the physiological, biophysical and biochemical level. THE NEW PHYTOLOGIST 2010; 185:173-88. [PMID: 19863729 DOI: 10.1111/j.1469-8137.2009.03068.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
As the nonheterocystous diazotrophic cyanobacterium Trichodesmium lives both at the ocean surface and deep in the water column, it has to acclimate to vastly different irradiances. Here, we investigate its strategy of light acclimation in several ways. In this study, we used spectrally resolved fluorescence kinetic microscopy to investigate the biophysics of photosynthesis in individual cells, analysed cell extracts for pigment and phycobiliprotein composition, measured nitrogenase activity and the abundance of key proteins, and assayed protein synthesis/degradation by radioactive labelling. After acclimation to high light, Trichodesmium grew faster at 1000 micromol m(-2) s(-1) than at 100 micromol m(-2) s(-1). This acclimation was associated with decreasing cell diameter, faster protein turnover, the down-regulation of light-harvesting pigments and the outer part of the phycobiliprotein antenna, the up-regulation of light-protective carotenoids, changes in the coupling of phycobilisomes to the reaction centres and in the coupling of individual phycobiliproteins to the phycobilisomes. The latter was particularly interesting, as it represents an as yet unreported light acclimation strategy. Only in the low light-acclimated culture and only after the onset of actinic light did phycourobilin and phycoerythrin contribute to photochemical fluorescence quenching, showing that these phycobiliproteins may become quickly (in seconds) very closely coupled to photosystem II. This fast reversible coupling also became visible in the nonphotochemical changes of the fluorescence quantum yield.
Collapse
Affiliation(s)
- Elisa Andresen
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D78457 Konstanz, Germany
| | | | | | | | | | | |
Collapse
|
33
|
Cisek R, Spencer L, Prent N, Zigmantas D, Espie GS, Barzda V. Optical microscopy in photosynthesis. PHOTOSYNTHESIS RESEARCH 2009; 102:111-41. [PMID: 19851883 DOI: 10.1007/s11120-009-9500-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 10/05/2009] [Indexed: 05/03/2023]
Abstract
Emerging as well as the most frequently used optical microscopy techniques are reviewed and image contrast generation methods in a microscope are presented, focusing on the nonlinear contrasts such as harmonic generation and multiphoton excitation fluorescence. Nonlinear microscopy presents numerous advantages over linear microscopy techniques including improved deep tissue imaging, optical sectioning, and imaging of live unstained samples. Nonetheless, with the exception of multiphoton excitation fluorescence, nonlinear microscopy is in its infancy, lacking protocols, users and applications; hence, this review focuses on the potential of nonlinear microscopy for studying photosynthetic organisms. Examples of nonlinear microscopic imaging are presented including isolated light-harvesting antenna complexes from higher plants, starch granules, chloroplasts, unicellular alga Chlamydomonas reinhardtii, and cyanobacteria Leptolyngbya sp. and Anabaena sp. While focusing on nonlinear microscopy techniques, second and third harmonic generation and multiphoton excitation fluorescence microscopy, other emerging nonlinear imaging modalities are described and several linear optical microscopy techniques are reviewed in order to clearly describe their capabilities and to highlight the advantages of nonlinear microscopy.
Collapse
Affiliation(s)
- Richard Cisek
- Department of Chemical and Physical Sciences, University of Toronto, 3359 Mississauga Road, Mississauga, ON, L5L 1C6, Canada
| | | | | | | | | | | |
Collapse
|
34
|
Kelman D, Ben-Amotz A, Berman-Frank I. Carotenoids provide the major antioxidant defence in the globally significant N2-fixing marine cyanobacterium Trichodesmium. Environ Microbiol 2009; 11:1897-908. [PMID: 19397682 DOI: 10.1111/j.1462-2920.2009.01913.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosynthetic oxygen-evolving microorganisms contend with continuous self-production of molecular oxygen and reactive oxygen species. The deleterious effects of reactive oxygen species are exacerbated for cyanobacterial nitrogen-fixers (diazotrophs) due to the innate sensitivity of nitrogenase to oxygen. This renders incompatible the processes of oxygen-evolving photosynthesis and N-fixation. We examined total antioxidative potential of various diazotrophic and non-diazotrophic cyanobacteria. We focused on Trichodesmium spp., a bloom-forming marine diazotroph that contributes significantly to global nitrogen fixation. Among the species tested, Trichodesmium possessed the highest antioxidant activity. Moreover, while proteins constituted the dominant antioxidative component of all other cyanobacteria tested, Trichodesmium was unique in that small-molecule natural products provided the majority of antioxidant activity, while proteins constituted only 13% of total antioxidant activity. Bioassay-guided fractionation followed by high-performance liquid chromatography profiling of antioxidant purified fractions identified the highly potent antioxidant all-trans-β-carotene, and small amounts of 9-cis-β-carotene and retinyl palmitate. Search of the Trichodesmium genome identified protein sequences homologous to key enzymes in the β-carotene to retinyl palmitate biosynthetic pathway, including 33-37% identity to lecithin retinol acyltransferase. The present study demonstrates the importance of carotenoids in Trichodesmium's arsenal of defensive compounds against oxidative damage and protection of nitrogenase from oxygen and its radicals.
Collapse
Affiliation(s)
- Dovi Kelman
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan 52900, Israel.
| | | | | |
Collapse
|
35
|
Stal LJ. Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature? Environ Microbiol 2009; 11:1632-45. [PMID: 19397684 DOI: 10.1111/j.1758-2229.2009.00016.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A-C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas.
Collapse
Affiliation(s)
- Lucas J Stal
- Department of Marine Microbiology, Netherlands Institute of Ecology, NIOO-KNAW, POBox 140, 4400 AC Yerseke, The Netherlands.
| |
Collapse
|
36
|
Fixation and fate of C and N in the cyanobacterium Trichodesmium using nanometer-scale secondary ion mass spectrometry. Proc Natl Acad Sci U S A 2009; 106:6345-50. [PMID: 19332780 DOI: 10.1073/pnas.0810547106] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The marine cyanobacterium Trichodesmium is ubiquitous in tropical and subtropical seas and is an important contributor to global N and C cycling. We sought to characterize metabolic uptake patterns in individual Trichodesmium IMS-101 cells by quantitatively imaging (13)C and (15)N uptake with high-resolution secondary ion mass spectrometry (NanoSIMS). Trichodesmium fix both CO(2) and N(2) concurrently during the day and are, thus, faced with a balancing act: the O(2) evolved during photosynthesis inhibits nitrogenase, the key enzyme in N(2) fixation. After performing correlated transmission electron microscopy (TEM) and NanoSIMS analysis on trichome thin-sections, we observed transient inclusion of (15)N and (13)C into discrete subcellular bodies identified as cyanophycin granules. We speculate that Trichodesmium uses these dynamic storage bodies to uncouple CO(2) and N(2) fixation from overall growth dynamics. We also directly quantified both CO(2) and N(2) fixation at the single cell level using NanoSIMS imaging of whole cells in multiple trichomes. Our results indicate maximal CO(2) fixation rates in the morning, compared with maximal N(2) fixation rates in the afternoon, bolstering the argument that segregation of CO(2) and N(2) fixation in Trichodesmium is regulated in part by temporal factors. Spatial separation of N(2) and CO(2) fixation may also have a role in metabolic segregation in Trichodesmium. Our approach in combining stable isotope labeling with NanoSIMS and TEM imaging can be extended to other physiologically relevant elements and processes in other important microbial systems.
Collapse
|
37
|
Küpper H, Andresen E, Wiegert S, Šimek M, Leitenmaier B, Šetlík I. Reversible coupling of individual phycobiliprotein isoforms during state transitions in the cyanobacterium Trichodesmium analysed by single-cell fluorescence kinetic measurements. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:155-67. [DOI: 10.1016/j.bbabio.2009.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2008] [Revised: 01/05/2009] [Accepted: 01/05/2009] [Indexed: 11/28/2022]
|
38
|
Küpper H, Šetlík I, Seibert S, Prášil O, Šetlikova E, Strittmatter M, Levitan O, Lohscheider J, Adamska I, Berman-Frank I. Iron limitation in the marine cyanobacterium Trichodesmium reveals new insights into regulation of photosynthesis and nitrogen fixation. THE NEW PHYTOLOGIST 2008; 179:784-798. [PMID: 18513224 DOI: 10.1111/j.1469-8137.2008.02497.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
* As iron (Fe) deficiency is a main limiting factor of ocean productivity, its effects were investigated on interactions between photosynthesis and nitrogen fixation in the marine nonheterocystous diazotrophic cyanobacterium Trichodesmium IMS101. * Biophysical methods such as fluorescence kinetic microscopy, fast repetition rate (FRR) fluorimetry, and in vivo and in vitro spectroscopy of pigment composition were used, and nitrogenase activity and the abundance of key proteins were measured. * Fe limitation caused a fast down-regulation of nitrogenase activity and protein levels. By contrast, the abundance of Fe-requiring photosystem I (PSI) components remained constant. Total levels of phycobiliproteins remained unchanged according to single-cell in vivo spectra. However, the regular 16-kDa phycoerythrin band decreased and finally disappeared 16-20 d after initiation of Fe limitation, concomitant with the accumulation of a 20-kDa protein cross-reacting with the phycoerythrin antibody. Concurrently, nitrogenase expression and activity increased. Fe limitation dampened the daily cycle of photosystem II (PSII) activity characteristic of diazotrophic Trichodesmium cells. Further, it increased the number and prolonged the time period of occurrence of cells with elevated basic fluorescence (F(0)). Additionally, it increased the effective cross-section of PSII, probably as a result of enhanced coupling of phycobilisomes to PSII, and led to up-regulation of the Fe stress protein IsiA. * Trichodesmium survives short-term Fe limitation by selectively down-regulating nitrogen fixation while maintaining but re-arranging the photosynthetic apparatus.
Collapse
Affiliation(s)
- Hendrik Küpper
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany
- University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic
| | - Ivan Šetlík
- University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic
- Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic
| | - Sven Seibert
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany
| | - Ondrej Prášil
- University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic
- Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic
| | - Eva Šetlikova
- University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic
- Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic
| | - Martina Strittmatter
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany
| | - Orly Levitan
- Bar Ilan University, Mina and Everard Goodman Faculty of Life Sciences, Ramat Gan, 52900, Israel
| | - Jens Lohscheider
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany
| | - Iwona Adamska
- Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany
| | - Ilana Berman-Frank
- Bar Ilan University, Mina and Everard Goodman Faculty of Life Sciences, Ramat Gan, 52900, Israel
| |
Collapse
|
39
|
Küpper H, Seibert S, Parameswaran A. Fast, Sensitive, and Inexpensive Alternative to Analytical Pigment HPLC: Quantification of Chlorophylls and Carotenoids in Crude Extracts by Fitting with Gauss Peak Spectra. Anal Chem 2007; 79:7611-27. [PMID: 17854156 DOI: 10.1021/ac070236m] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantification of pigments in complex mixtures is an important task in the physiology of photosynthetic organisms, because pigment composition differs depending on the species, tissue, and physiological state. Currently available methods, however, are either limited to very few pigments (classical UV/vis spectroscopic methods), or they are time-consuming, labor intensive, or costly (e.g., HPLC). Here we describe a UV/vis spectrophotometric method that is capable of a rapid (approximately 1 min/sample) and inexpensive (<1 euro/sample) quantification of more than a dozen pigments in a crude extract, which means it is suitable for high-throughput screening applications. A detection limit of <1 pmol for each pigment allows for determining the pigment composition in only 0.5 microg of lyophilized leaves or algae. The method is based on the description of each pigment spectrum by a series of Gaussian peaks. A sample spectrum is then fitted by a linear combination of these "Gauss peak spectra" including an automatic correction of wavelength inaccuracy, baseline instability, sample turbidity, and effects of temperature/water content. Here we present the Gauss peak spectra from 350 to 750 nm for acetone solutions of all chlorophyll and carotenoid derivatives that are abundant (including conditions of Cd, Cu, or Zn stress) in leaves of higher plants, Euglena, brown algae, and various cyanobacteria like Anabaena and Trichodesmium: [Mg]-Chl a, b, c1, c2; pheophytin a, b; [Cd]-Chl a, b; [Cu]-Chl a, b; [Zn]-Chl a, b; antheraxanthin, aurochrome, beta-carotene, beta-cryptoxanthin, cis- and trans-canthaxanthin, diadinochrome (=diadinoxanthin 5,6-epoxide), cis- and trans-diadinoxanthin, diatoxanthin, cis- and trans-echinenone, fucoxanthin, lutein, myxoxanthophyll, neoxanthin, violaxanthin, and all three stereoisomers of zeaxanthin in acetone. We present extensive tests of our new quantification method for determining optimal and limiting conditions of its performance and for comparison with previous methods. Finally, we show application examples for Thlaspi fendleri (Chlorophyta), Euglena gracilisc (Euglenophyta), Ectocarpus siliculosus (Phaeophyta), and Trichodesmium erythraeum IMS101 (cyanobacteria).
Collapse
Affiliation(s)
- Hendrik Küpper
- Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, Universität Konstanz, D-78457 Konstanz, Germany.
| | | | | |
Collapse
|
40
|
Staal M, Rabouille S, Stal LJ. On the role of oxygen for nitrogen fixation in the marine cyanobacterium Trichodesmium sp. Environ Microbiol 2007; 9:727-36. [PMID: 17298372 DOI: 10.1111/j.1462-2920.2006.01195.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The marine, non-heterocystous, filamentous cyanobacterium Trichodesmium shows a distinct diurnal pattern of nitrogenase activity. In an attempt to reveal the factors that control this pattern, a series of measurements were carried out using online acetylene reduction assay. Light response curves of nitrogenase were recorded applying various concentrations of oxygen. The effect of oxygen depended on the irradiance applied. Above a photon irradiance of 16 mumol m(-2) s(-1) nitrogenase activity was highest under anoxic conditions. Below this irradiance the presence of oxygen was required to achieve highest nitrogenase activity and in the dark 5% oxygen was optimal. At any oxygen concentration a photon irradiance of 100 mumol m(-2) s(-1) was saturating. When Trichodesmium was incubated in the dark, nitrogenase activity gradually decreased and this decline was higher at higher levels of oxygen. The activity recovered when the cells were subsequently incubated in the light. This recovery depended on oxygenic photosynthesis because it did not occur in the presence of DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea]. Recovery of nitrogenase activity in the light was faster at low oxygen concentrations. The results showed that under aerobic conditions nitrogenase activity was limited by the availability of reducing equivalents suggesting a competition for electrons between nitrogenase and respiration.
Collapse
Affiliation(s)
- Marc Staal
- Netherlands Institute of Ecology, NIOO-KNAW, Centre for Estuarine and Marine Ecology, P.O. Box 140, 4400 AC Yerseke, the Netherlands
| | | | | |
Collapse
|
41
|
Vácha F, Sarafis V, Benediktyová Z, Bumba L, Valenta J, Vácha M, Sheue CR, Nedbal L. Identification of Photosystem I and Photosystem II enriched regions of thylakoid membrane by optical microimaging of cryo-fluorescence emission spectra and of variable fluorescence. Micron 2007; 38:170-5. [PMID: 16962333 DOI: 10.1016/j.micron.2006.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oxygenic photosynthesis of higher plants requires linear electron transport that is driven by serially operating Photosystem II and Photosystem I reaction centers. It is widely accepted that distribution of these two types of reaction centers in the thylakoid membrane is heterogeneous. Here, we describe two optical microscopic techniques that can be combined to reveal the heterogeneity. By imaging micro-spectroscopy at liquid nitrogen temperature, we resolved the heterogeneity of the chloroplast thylakoid membrane by distinct spectral signatures of fluorescence emitted by the two photosystems. With another microscope, we measured changes in the fluorescence emission yield that are induced by actinic light at room temperature. Fluorescence yield of Photosystem II reaction centers varies strongly with light-induced changes of its photochemical yield. Consequently, application of moderate background irradiance induces changes in the Photosystem II fluorescence yield whereas no such modulation occurs in Photosystem I. This contrasting feature was used to identify regions in thylakoid membranes that are enriched in active Photosystem II.
Collapse
Affiliation(s)
- F Vácha
- Institute of Physical Biology, University of South Bohemia, Zámek 136, 37333 Nové Hrady, Czech Republic
| | | | | | | | | | | | | | | |
Collapse
|