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Masuda T, Mareš J, Shiozaki T, Inomura K, Fujiwara A, Prášil O. Crocosphaera watsonii - A widespread nitrogen-fixing unicellular marine cyanobacterium. JOURNAL OF PHYCOLOGY 2024; 60:604-620. [PMID: 38551849 DOI: 10.1111/jpy.13450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 12/14/2023] [Accepted: 02/08/2024] [Indexed: 06/12/2024]
Abstract
Crocosphaera watsonii is a unicellular N2-fixing (diazotrophic) cyanobacterium observed in tropical and subtropical oligotrophic oceans. As a diazotroph, it can be a source of bioavailable nitrogen (N) to the microbial community in N-limited environments, and this may fuel primary production in the regions where it occurs. Crocosphaera watsonii has been the subject of intense study, both in culture and in field populations. Here, we summarize the current understanding of the phylogenetic and physiological diversity of C. watsonii, its distribution, and its ecological niche. Analysis of the relationships among the individual Crocosphaera species and related free-living and symbiotic lineages of diazotrophs based on the nifH gene have shown that the C. watsonii group holds a basal position and that its sequence is more similar to Rippkaea and Zehria than to other Crocosphaera species. This finding warrants further scrutiny to determine if the placement is related to a horizontal gene transfer event. Here, the nifH UCYN-B gene copy number from a recent synthesis effort was used as a proxy for relative C. watsonii abundance to examine patterns of C. watsonii distribution as a function of environmental factors, like iron and phosphorus concentration, and complimented with a synthesis of C. watsonii physiology. Furthermore, we have summarized the current knowledge of C. watsonii with regards to N2 fixation, photosynthesis, and quantitative modeling of physiology. Because N availability can limit primary production, C. watsonii is widely recognized for its importance to carbon and N cycling in ocean ecosystems, and we conclude this review by highlighting important topics for further research on this important species.
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Affiliation(s)
- Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
- Japan Fisheries Research and Education Agency, Shiogama, Miyagi, Japan
| | - Jan Mareš
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
- Institute of Hydrobiology, Biology Centre, The Czech Academy of Sciences, České Budejovice, Czech Republic
| | - Takuhei Shiozaki
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA
| | - Amane Fujiwara
- Research Institute for Global Change, JAMSTEC, Yokosuka, Japan
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
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Bandyopadhyay A, Sengupta A, Elvitigala T, Pakrasi HB. Endogenous clock-mediated regulation of intracellular oxygen dynamics is essential for diazotrophic growth of unicellular cyanobacteria. Nat Commun 2024; 15:3712. [PMID: 38697963 PMCID: PMC11065991 DOI: 10.1038/s41467-024-48039-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/16/2024] [Indexed: 05/05/2024] Open
Abstract
The discovery of nitrogen fixation in unicellular cyanobacteria provided the first clues for the existence of a circadian clock in prokaryotes. However, recalcitrance to genetic manipulation barred their use as model systems for deciphering the clock function. Here, we explore the circadian clock in the now genetically amenable Cyanothece 51142, a unicellular, nitrogen-fixing cyanobacterium. Unlike non-diazotrophic clock models, Cyanothece 51142 exhibits conspicuous self-sustained rhythms in various discernable phenotypes, offering a platform to directly study the effects of the clock on the physiology of an organism. Deletion of kaiA, an essential clock component in the cyanobacterial system, impacted the regulation of oxygen cycling and hindered nitrogenase activity. Our findings imply a role for the KaiA component of the clock in regulating the intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria and suggest that its addition to the KaiBC clock was likely an adaptive strategy that ensured optimal nitrogen fixation as microbes evolved from an anaerobic to an aerobic atmosphere under nitrogen constraints.
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Affiliation(s)
| | - Annesha Sengupta
- Department of Biology, Washington University, St. Louis, MO, USA
- Department of Chemical Engineering, University of Toronto, Toronto, ON, Canada
| | - Thanura Elvitigala
- Department of Biology, Washington University, St. Louis, MO, USA
- General Motors Research and Development, Warren, MI, 48092, USA
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3
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Masuda T, Bečková M, Turóczy Z, Pilný J, Sobotka R, Trinugroho JP, Nixon PJ, Prášil O, Komenda J. Accumulation of Cyanobacterial Photosystem II Containing the 'Rogue' D1 Subunit Is Controlled by FtsH Protease and Synthesis of the Standard D1 Protein. PLANT & CELL PHYSIOLOGY 2023; 64:660-673. [PMID: 36976618 DOI: 10.1093/pcp/pcad027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 03/24/2023] [Accepted: 03/27/2023] [Indexed: 06/16/2023]
Abstract
Unicellular diazotrophic cyanobacteria contribute significantly to the photosynthetic productivity of the ocean and the fixation of molecular nitrogen, with photosynthesis occurring during the day and nitrogen fixation during the night. In species like Crocosphaera watsonii WH8501, the decline in photosynthetic activity in the night is accompanied by the disassembly of oxygen-evolving photosystem II (PSII) complexes. Moreover, in the second half of the night phase, a small amount of rogue D1 (rD1), which is related to the standard form of the D1 subunit found in oxygen-evolving PSII, but of unknown function, accumulates but is quickly degraded at the start of the light phase. We show here that the removal of rD1 is independent of the rD1 transcript level, thylakoid redox state and trans-thylakoid pH but requires light and active protein synthesis. We also found that the maximal level of rD1 positively correlates with the maximal level of chlorophyll (Chl) biosynthesis precursors and enzymes, which suggests a possible role for rogue PSII (rPSII) in the activation of Chl biosynthesis just before or upon the onset of light, when new photosystems are synthesized. By studying strains of Synechocystis PCC 6803 expressing Crocosphaera rD1, we found that the accumulation of rD1 is controlled by the light-dependent synthesis of the standard D1 protein, which triggers the fast FtsH2-dependent degradation of rD1. Affinity purification of FLAG-tagged rD1 unequivocally demonstrated the incorporation of rD1 into a non-oxygen-evolving PSII complex, which we term rPSII. The complex lacks the extrinsic proteins stabilizing the oxygen-evolving Mn4CaO5 cluster but contains the Psb27 and Psb28-1 assembly factors.
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Affiliation(s)
- Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
| | - Martina Bečková
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
| | - Zoltán Turóczy
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
| | - Jan Pilný
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
| | - Roman Sobotka
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice 370 05, Czech Republic
| | - Joko P Trinugroho
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Peter J Nixon
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
| | - Josef Komenda
- Institute of Microbiology, The Czech Academy of Sciences, Centre Algatech, Opatovický mlýn, Třeboň 37901, Czech Republic
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice 370 05, Czech Republic
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Masuda T, Inomura K, Gao M, Armin G, Kotabová E, Bernát G, Lawrenz-Kendrick E, Lukeš M, Bečková M, Steinbach G, Komenda J, Prášil O. The balance between photosynthesis and respiration explains the niche differentiation between Crocosphaera and Cyanothece. Comput Struct Biotechnol J 2022; 21:58-65. [PMID: 36514336 PMCID: PMC9732122 DOI: 10.1016/j.csbj.2022.11.029] [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: 10/14/2022] [Revised: 11/12/2022] [Accepted: 11/13/2022] [Indexed: 11/18/2022] Open
Abstract
Crocosphaera and Cyanothece are both unicellular, nitrogen-fixing cyanobacteria that prefer different environments. Whereas Crocosphaera mainly lives in nutrient-deplete, open oceans, Cyanothece is more common in coastal, nutrient-rich regions. Despite their physiological similarities, the factors separating their niches remain elusive. Here we performed physiological experiments on clone cultures and expand upon a simple ecological model to show that their different niches can be sufficiently explained by the observed differences in their photosynthetic capacities and rates of carbon (C) consumption. Our experiments revealed that Cyanothece has overall higher photosynthesis and respiration rates than Crocosphaera. A simple growth model of these microorganisms suggests that C storage and consumption are previously under-appreciated factors when evaluating the occupation of niches by different marine nitrogen fixers.
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Affiliation(s)
- Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic,Corresponding authors.
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
| | - Meng Gao
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
| | - Gabrielle Armin
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
| | - Eva Kotabová
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic
| | - Gábor Bernát
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic,Balaton Limnological Research Institute, Eötvös Loránd Research Network (ELKH), Tihany, Hungary
| | - Evelyn Lawrenz-Kendrick
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic
| | - Martin Lukeš
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic
| | - Martina Bečková
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic
| | - Gábor Steinbach
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic,Cellular Imaging Laboratory, Biological Research Center, Eötvös Loránd Research Network (ELKH), Szeged, Hungary
| | - Josef Komenda
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 37901 Třeboň, Czech Republic,Corresponding authors.
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Photosynthetic modulation during the diurnal cycle in a unicellular diazotrophic cyanobacterium grown under nitrogen-replete and nitrogen-fixing conditions. Sci Rep 2022; 12:18939. [PMID: 36344535 PMCID: PMC9640542 DOI: 10.1038/s41598-022-21829-6] [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: 07/25/2022] [Accepted: 10/04/2022] [Indexed: 11/09/2022] Open
Abstract
Cyanobacteria are the only oxygenic photosynthetic organisms that can fix nitrogen. In diazotrophic cyanobacteria, the regulation of photosynthesis during the diurnal cycle is hypothesized to be linked with nitrogen fixation and involve the D1 protein isoform PsbA4. The amount of bioavailable nitrogen has a major impact on productivity in aqueous environments. In contrast to low- or nitrogen-fixing (-N) conditions, little data on photosynthetic regulation under nitrogen-replete (+ N) conditions are available. We compared the regulation of photosynthesis under -N and + N conditions during the diurnal cycle in wild type and a psbA4 deletion strain of the unicellular diazotrophic cyanobacterium Cyanothece sp. ATCC 51142. We observed common changes to light harvesting and photosynthetic electron transport during the dark in + N and -N conditions and found that these modifications occur in both diazotrophic and non-diazotrophic cyanobacteria. Nitrogen availability increased PSII titer when cells transitioned from dark to light and promoted growth. Under -N conditions, deletion of PsbA4 modified charge recombination in dark and regulation of PSII titer during dark to light transition. We conclude that darkness impacts the acceptor-side modifications to PSII and photosynthetic electron transport in cyanobacteria independently of the nitrogen-fixing status and the presence of PsbA4.
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6
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A Novel Algicidal Bacterium and Its Effects against the Toxic Dinoflagellate Karenia mikimotoi (Dinophyceae). Microbiol Spectr 2022; 10:e0042922. [PMID: 35616372 PMCID: PMC9241683 DOI: 10.1128/spectrum.00429-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The toxic dinoflagellate Karenia mikimotoi is a harmful algal bloom-forming species in coastal areas around the world. It produces ichthyotoxins and hemolytic toxins, with deleterious effects on marine ecosystems. In this study, the bacterium Pseudoalteromonas sp. FDHY-MZ2, with high algicidal efficiency against K. mikimotoi, was isolated from a bloom event. Based on the results, it completely lysed K. mikimotoi cells within 24 h 0.5% (vol/vol), with the algicidal activity of the supernatant of the bacterium culture. Algal cell wall fragmentation occurred, leading to cell death. There was a marked decline in various photochemical traits. When treated with the supernatant, cellulase, pheophorbide a oxygenase (PAO) and cyclin B genes were significantly increased, suggesting induced cell wall deterioration, chloroplast degradation and cell cycle regulation of K. mikimotoi cells. In addition, the expression levels of reactive oxygen species (ROS) scavenging gene was significantly inhibited, indicating that the ROS removal system was damaged. The bacterial culture was dried to obtain the spray-dried powder, which showed algicidal activity rates of 92.2 and 100% against a laboratory K. mikimotoi culture and a field microcosm of Karlodinium sp. bloom within 24 h with the addition of 0.04% mass fraction powder. Our results demonstrate that FDHY-MZ2 is a suitable strain for K. mikimotoi and Karlodinium sp. blooms management. In addition, this study provides a new strategy for the anthropogenic control of harmful algal bloom-forming species in situ. IMPORTANCE K. mikimotoi is a noxious algal bloom-forming species that cause damaging of the aquaculture industry and great financial losses. Bacterium with algicidal activity is an ideal agency to inhibit the growth of harmful algae. In this approach application, the bacterium with high algicidal activity is required and the final management material is ideal for easy-to-use. The algicidal characteristics are also needed to understand the effects of the bacterium for managing strategy exploration. In this study, we isolated a novel algicidal bacterium with extremely high lysis efficiency for K. mikimotoi. The algicidal characteristics of the bacterium as well as the chemical and molecular response of K. mikimotoi with the strain challenge were examined. Finally, the algicidal powder was explored for application. The results demonstrate that FDHY-MZ2 is suitable for K. mikimotoi and Karlodinium sp. blooms controlling, and this study provides a new strategy for algicidal bacterium application.
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7
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Cyclophilin anaCyp40 regulates photosystem assembly and phycobilisome association in a cyanobacterium. Nat Commun 2022; 13:1690. [PMID: 35354803 PMCID: PMC8967839 DOI: 10.1038/s41467-022-29211-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 02/28/2022] [Indexed: 11/08/2022] Open
Abstract
Cyclophilins, or immunophilins, are proteins found in many organisms including bacteria, plants and humans. Most of them display peptidyl-prolyl cis-trans isomerase activity, and play roles as chaperones or in signal transduction. Here, we show that cyclophilin anaCyp40 from the cyanobacterium Anabaena sp. PCC 7120 is enzymatically active, and seems to be involved in general stress responses and in assembly of photosynthetic complexes. The protein is associated with the thylakoid membrane and interacts with phycobilisome and photosystem components. Knockdown of anacyp40 leads to growth defects under high-salt and high-light conditions, and reduced energy transfer from phycobilisomes to photosystems. Elucidation of the anaCyp40 crystal structure at 1.2-Å resolution reveals an N-terminal helical domain with similarity to PsbQ components of plant photosystem II, and a C-terminal cyclophilin domain with a substrate-binding site. The anaCyp40 structure is distinct from that of other multi-domain cyclophilins (such as Arabidopsis thaliana Cyp38), and presents features that are absent in single-domain cyclophilins.
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8
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Masuda T, Inomura K, Mareš J, Prášil O. Crocosphaera watsonii. Trends Microbiol 2022; 30:805-806. [PMID: 35331632 DOI: 10.1016/j.tim.2022.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 11/27/2022]
Affiliation(s)
- Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 379 01 Třeboň, Czech Republic.
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Jan Mareš
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 379 01 Třeboň, Czech Republic; Biology Centre of the Czech Academy of Sciences, Institute of Hydrobiology, Na Sádkách 702/7, 370 05 České Budějovice, Czech Republic
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Opatovický mlýn, 379 01 Třeboň, Czech Republic
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Marcarelli AM, Fulweiler RW, Scott JT. Nitrogen fixation: a poorly understood process along the freshwater-marine continuum. LIMNOLOGY AND OCEANOGRAPHY LETTERS 2022; 7:1-10. [PMID: 35531372 PMCID: PMC9075158 DOI: 10.1002/lol2.10220] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 10/08/2021] [Indexed: 06/14/2023]
Abstract
Although N2 fixation is a major component of the global N cycle and has been extensively studied in open-ocean and terrestrial ecosystems, rates and ecological dynamics remain virtually unknown for the inland and coastal aquatic ecosystems (lakes, wetlands, rivers, streams, estuaries) that connect terrestrial and marine biomes. This is due to the diversity of these habitats, as well as the traditional paradigm that N2 fixation rates were low to nonexistent, and therefore not important, in these ecosystems. We identify three major research themes to advance understanding of aquatic N2 fixation: 1) the biological diversity of diazotrophs and variability of N2 fixation rates, 2) the ecological stoichiometry of N2 fixation, and 3) the upscaling of N2 fixation rates from genes to ecosystems. Coordinating research across these areas will advance limnology and oceanography by fully integrating N2 fixation into ecological dynamics of aquatic ecosystems from local to global scales.
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Affiliation(s)
- Amy M. Marcarelli
- Department of Biological Sciences, Michigan Technological University
| | - Robinson W. Fulweiler
- Department of Earth and Environment, Boston University
- Department of Biology, Boston University
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10
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Inomura K, Masuda T, Eichner M, Rabouille S, Zavřel T, Červený J, Vancová M, Bernát G, Armin G, Claquin P, Kotabová E, Stephan S, Suggett DJ, Deutsch C, Prášil O. Quantifying Cyanothece growth under DIC limitation. Comput Struct Biotechnol J 2021; 19:6456-6464. [PMID: 34938417 PMCID: PMC8665340 DOI: 10.1016/j.csbj.2021.11.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 11/22/2021] [Accepted: 11/22/2021] [Indexed: 11/26/2022] Open
Abstract
The photoautotrophic, unicellular N2-fixer, Cyanothece, is a model organism that has been widely used to study photosynthesis regulation, the structure of photosystems, and the temporal segregation of carbon (C) and nitrogen (N) fixation in light and dark phases of the diel cycle. Here, we present a simple quantitative model and experimental data that together, suggest external dissolved inorganic carbon (DIC) concentration as a major limiting factor for Cyanothece growth, due to its high C-storage requirement. Using experimental data from a parallel laboratory study as a basis, we show that after the onset of the light period, DIC was rapidly consumed by photosynthesis, leading to a sharp drop in the rate of photosynthesis and C accumulation. In N2-fixing cultures, high rates of photosynthesis in the morning enabled rapid conversion of DIC to intracellular C storage, hastening DIC consumption to levels that limited further uptake. The N2-fixing condition allows only a small fraction of fixed C for cellular growth since a large fraction was reserved in storage to fuel night-time N2 fixation. Our model provides a framework for resolving DIC limitation in aquatic ecosystem simulations, where DIC as a growth-limiting factor has rarely been considered, and importantly emphasizes the effect of intracellular C allocation on growth rate that varies depending on the growth environment.
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Affiliation(s)
- Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA
| | - Takako Masuda
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
| | - Meri Eichner
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
| | - Sophie Rabouille
- Sorbonne Université, CNRS, Laboratoire d'Océanographie Microbienne, LOMIC, F-66650 Banyuls-sur-mer, France
| | - Tomáš Zavřel
- Department of Adaptive Biotechnologies, Global Change Research Institute, Czech Academy of Sciences, Brno, Czech Republic
| | - Jan Červený
- Department of Adaptive Biotechnologies, Global Change Research Institute, Czech Academy of Sciences, Brno, Czech Republic
| | - Marie Vancová
- Laboratory of Electron Microscopy, Institute of Parasitology, Biology Centre of the Czech Academy of Sciences and Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Gábor Bernát
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic.,Balaton Limnological Research Institute, Eötvös Loránd Research Network (ELKH), Tihany, Hungary
| | - Gabrielle Armin
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA
| | - Pascal Claquin
- Laboratoire de Biologie des ORganismes et Ecosystèmes Aquatiques (BOREA), UMR 8067, Muséum National d'Histoire Naturelle, CNRS, IRD Sorbonne Université, Université de Caen Normandie, Normandie Université, Esplanade de la Paix, F-14032 Caen, France
| | - Eva Kotabová
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
| | - Susanne Stephan
- Department Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
| | - David J Suggett
- University of Technology Sydney, Climate Change Cluster, Faculty of Science, Ultimo, NSW 2007, Australia
| | - Curtis Deutsch
- School of Oceanography, University of Washington, Seattle, WA, USA
| | - Ondřej Prášil
- Institute of Microbiology, The Czech Academy of Sciences, Třeboň, Czech Republic
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11
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Rabouille S, Campbell DA, Masuda T, Zavřel T, Bernát G, Polerecky L, Halsey K, Eichner M, Kotabová E, Stephan S, Lukeš M, Claquin P, Bonomi-Barufi J, Lombardi AT, Červený J, Suggett DJ, Giordano M, Kromkamp JC, Prášil O. Electron & Biomass Dynamics of Cyanothece Under Interacting Nitrogen & Carbon Limitations. Front Microbiol 2021; 12:617802. [PMID: 33897635 PMCID: PMC8063122 DOI: 10.3389/fmicb.2021.617802] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 03/01/2021] [Indexed: 11/25/2022] Open
Abstract
Marine diazotrophs are a diverse group with key roles in biogeochemical fluxes linked to primary productivity. The unicellular, diazotrophic cyanobacterium Cyanothece is widely found in coastal, subtropical oceans. We analyze the consequences of diazotrophy on growth efficiency, compared to NO3–-supported growth in Cyanothece, to understand how cells cope with N2-fixation when they also have to face carbon limitation, which may transiently affect populations in coastal environments or during blooms of phytoplankton communities. When grown in obligate diazotrophy, cells face the double burden of a more ATP-demanding N-acquisition mode and additional metabolic losses imposed by the transient storage of reducing potential as carbohydrate, compared to a hypothetical N2 assimilation directly driven by photosynthetic electron transport. Further, this energetic burden imposed by N2-fixation could not be alleviated, despite the high irradiance level within the cultures, because photosynthesis was limited by the availability of dissolved inorganic carbon (DIC), and possibly by a constrained capacity for carbon storage. DIC limitation exacerbates the costs on growth imposed by nitrogen fixation. Therefore, the competitive efficiency of diazotrophs could be hindered in areas with insufficient renewal of dissolved gases and/or with intense phytoplankton biomass that both decrease available light energy and draw the DIC level down.
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Affiliation(s)
- Sophie Rabouille
- Sorbonne Université, CNRS, LOV, Villefranche-sur-Mer, France.,Sorbonne Université, CNRS, LOMIC, Banyuls-sur-Mer, France
| | - Douglas A Campbell
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Mount Allison University, Sackville, NB, Canada
| | - Takako Masuda
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Tomáš Zavřel
- Department of Adaptive Biotechnologies, Global Change Research Institute CAS, Brno, Czechia
| | - Gábor Bernát
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Centre for Ecological Research, Balaton Limnological Institute, Klebelsberg Kuno u. 3. 8237 Tihany, Hungary
| | - Lubos Polerecky
- Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
| | - Kimberly Halsey
- Department of Microbiology, Oregon State University, Corvallis, OR, United States
| | - Meri Eichner
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Eva Kotabová
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Susanne Stephan
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Zur alten Fischerhütte 2, Stechlin, Germany.,Department of Ecology, Berlin Institute of Technology (TU Berlin), Ernst-Reuter-Platz 1, Berlin, Germany
| | - Martin Lukeš
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
| | - Pascal Claquin
- UMR BOREA (CNRS 8067), MNHN, IRD (207), Université de Caen Basse-Normandie, Caen, France
| | - José Bonomi-Barufi
- Departamento de Botânica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | | | - Jan Červený
- Department of Adaptive Biotechnologies, Global Change Research Institute CAS, Brno, Czechia
| | - David J Suggett
- University of Technology Sydney, Climate Change Cluster, Faculty of Science, Ultimo, NSW, Australia
| | - Mario Giordano
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia.,Dipartimento di Scienze della Vita e dell'Ambiente, UniversitaÌ Politecnica delle Marche, Ancona, Italy
| | - Jacco C Kromkamp
- NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Utrecht, Netherlands
| | - Ondřej Prášil
- Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czechia
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12
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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.
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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
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13
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Sheridan KJ, Duncan EJ, Eaton-Rye JJ, Summerfield TC. The diversity and distribution of D1 proteins in cyanobacteria. PHOTOSYNTHESIS RESEARCH 2020; 145:111-128. [PMID: 32556852 DOI: 10.1007/s11120-020-00762-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
The psbA gene family in cyanobacteria encodes different forms of the D1 protein that is part of the Photosystem II reaction centre. We have identified a phylogenetically distinct D1 group that is intermediate between previously identified G3-D1 and G4-D1 proteins (Cardona et al. Mol Biol Evol 32:1310-1328, 2015). This new group contained two subgroups: D1INT, which was frequently in the genomes of heterocystous cyanobacteria and D1FR that was part of the far-red light photoacclimation gene cluster of cyanobacteria. In addition, we have identified subgroups within G3, the micro-aerobically expressed D1 protein. There are amino acid changes associated with each of the subgroups that might affect the function of Photosystem II. We show a phylogenetically broad range of cyanobacteria have these D1 types, as well as the genes encoding the G2 protein and chlorophyll f synthase. We suggest identification of additional D1 isoforms and the presence of multiple D1 isoforms in phylogenetically diverse cyanobacteria supports the role of these proteins in conferring a selective advantage under specific conditions.
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Affiliation(s)
- Kevin J Sheridan
- Department of Botany, University of Otago, Dunedin, New Zealand
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Elizabeth J Duncan
- Department of Biological Sciences, School of Biology, University of Leeds, Leeds, UK
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14
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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.
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15
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Trinugroho JP, Bečková M, Shao S, Yu J, Zhao Z, Murray JW, Sobotka R, Komenda J, Nixon PJ. Chlorophyll f synthesis by a super-rogue photosystem II complex. NATURE PLANTS 2020; 6:238-244. [PMID: 32170286 DOI: 10.1038/s41477-020-0616-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 02/06/2020] [Indexed: 05/21/2023]
Abstract
Certain cyanobacteria synthesize chlorophyll molecules (Chl d and Chl f) that absorb in the far-red region of the solar spectrum, thereby extending the spectral range of photosynthetically active radiation1,2. The synthesis and introduction of these far-red chlorophylls into the photosynthetic apparatus of plants might improve the efficiency of oxygenic photosynthesis, especially in far-red enriched environments, such as in the lower regions of the canopy3. Production of Chl f requires the ChlF subunit, also known as PsbA4 (ref. 4) or super-rogue D1 (ref. 5), a paralogue of the D1 subunit of photosystem II (PSII) which, together with D2, bind cofactors involved in the light-driven oxidation of water. Current ideas suggest that ChlF oxidizes Chl a to Chl f in a homodimeric ChlF reaction centre (RC) complex and represents a missing link in the evolution of the heterodimeric D1/D2 RC of PSII (refs. 4,6). However, unambiguous biochemical support for this proposal is lacking. Here, we show that ChlF can substitute for D1 to form modified PSII complexes capable of producing Chl f. Remarkably, mutation of just two residues in D1 converts oxygen-evolving PSII into a Chl f synthase. Overall, we have identified a new class of PSII complex, which we term 'super-rogue' PSII, with an unexpected role in pigment biosynthesis rather than water oxidation.
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Affiliation(s)
- Joko P Trinugroho
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Martina Bečková
- Laboratory of Photosynthesis, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Třeboň, Czech Republic
| | - Shengxi Shao
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Jianfeng Yu
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Ziyu Zhao
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - James W Murray
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK
| | - Roman Sobotka
- Laboratory of Photosynthesis, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Třeboň, Czech Republic
| | - Josef Komenda
- Laboratory of Photosynthesis, Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, Třeboň, Czech Republic
| | - Peter J Nixon
- Sir Ernst Chain Building-Wolfson Laboratories, Department of Life Sciences, Imperial College London, South Kensington Campus, London, UK.
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16
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Quantifying Oxygen Management and Temperature and Light Dependencies of Nitrogen Fixation by Crocosphaera watsonii. mSphere 2019; 4:4/6/e00531-19. [PMID: 31826967 PMCID: PMC6908418 DOI: 10.1128/msphere.00531-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Crocosphaera is a major dinitrogen (N2)-fixing microorganism, providing bioavailable nitrogen (N) to marine ecosystems. The N2-fixing enzyme nitrogenase is deactivated by oxygen (O2), which is abundant in marine environments. Using a cellular scale model of Crocosphaera sp. and laboratory data, we quantify the role of three O2 management strategies by Crocosphaera sp.: size adjustment, reduced O2 diffusivity, and respiratory protection. Our model predicts that Crocosphaera cells increase their size under high O2 Using transmission electron microscopy, we show that starch granules and thylakoid membranes are located near the cytoplasmic membranes, forming a barrier for O2 The model indicates a critical role for respiration in protecting the rate of N2 fixation. Moreover, the rise in respiration rates and the decline in ambient O2 with temperature strengthen this mechanism in warmer water, providing a physiological rationale for the observed niche of Crocosphaera at temperatures exceeding 20°C. Our new measurements of the sensitivity to light intensity show that the rate of N2 fixation reaches saturation at a lower light intensity (∼100 μmol m-2 s-1) than photosynthesis and that both are similarly inhibited by light intensities of >500 μmol m-2 s-1 This suggests an explanation for the maximum population of Crocosphaera occurring slightly below the ocean surface.IMPORTANCE Crocosphaera is one of the major N2-fixing microorganisms in the open ocean. On a global scale, the process of N2 fixation is important in balancing the N budget, but the factors governing the rate of N2 fixation remain poorly resolved. Here, we combine a mechanistic model and both previous and present laboratory studies of Crocosphaera to quantify how chemical factors such as C, N, Fe, and O2 and physical factors such as temperature and light affect N2 fixation. Our study shows that Crocosphaera combines multiple mechanisms to reduce intracellular O2 to protect the O2-sensitive N2-fixing enzyme. Our model, however, indicates that these protections are insufficient at low temperature due to reduced respiration and the rate of N2 fixation becomes severely limited. This provides a physiological explanation for why the geographic distribution of Crocosphaera is confined to the warm low-latitude ocean.
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17
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Active nitrogen fixation by Crocosphaera expands their niche despite the presence of ammonium - A case study. Sci Rep 2019; 9:15064. [PMID: 31636357 PMCID: PMC6803696 DOI: 10.1038/s41598-019-51378-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 09/30/2019] [Indexed: 11/09/2022] Open
Abstract
Unicellular nitrogen fixer Crocosphaera contributes substantially to nitrogen fixation in oligotrophic subtropical gyres. They fix nitrogen even when significant amounts of ammonium are available. This has been puzzling since fixing nitrogen is energetically inefficient compared with using available ammonium. Here we show that by fixing nitrogen, Crocosphaera can increase their population and expand their niche despite the presence of ammonium. We have developed a simple but mechanistic model of Crocosphaera based on their growth in steady state culture. The model shows that the growth of Crocosphaera can become nitrogen limited despite their capability to fix nitrogen. When they fix nitrogen, the population increases by up to 78% relative to the case without nitrogen fixation. When we simulate a simple ecological situation where Crocosphaera exists with non-nitrogen-fixing phytoplankton, the relative abundance of Crocosphaera increases with nitrogen fixation, while the population of non-nitrogen-fixing phytoplankton decreases since a larger fraction of fixed nitrogen is consumed by Crocosphaera. Our study quantitatively supports the benefit of nitrogen fixation despite the high electron/energy costs, even when an energetically efficient alternative is available. It demonstrates a competitive aspect of Crocosphaera, permitting them to be regionally significant nitrogen fixers.
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18
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Davenport EJ, Neudeck MJ, Matson PG, Bullerjahn GS, Davis TW, Wilhelm SW, Denney MK, Krausfeldt LE, Stough JMA, Meyer KA, Dick GJ, Johengen TH, Lindquist E, Tringe SG, McKay RML. Metatranscriptomic Analyses of Diel Metabolic Functions During a Microcystis Bloom in Western Lake Erie (United States). Front Microbiol 2019; 10:2081. [PMID: 31551998 PMCID: PMC6746948 DOI: 10.3389/fmicb.2019.02081] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 08/23/2019] [Indexed: 12/02/2022] Open
Abstract
This study examined diel shifts in metabolic functions of Microcystis spp. during a 48-h Lagrangian survey of a toxin-producing cyanobacterial bloom in western Lake Erie in the aftermath of the 2014 Toledo Water Crisis. Transcripts mapped to the genomes of recently sequenced lower Great Lakes Microcystis isolates showed distinct patterns of gene expression between samples collected across day (10:00 h, 16:00 h) and night (22:00 h, 04:00 h). Daytime transcripts were enriched in functions related to Photosystem II (e.g., psbA), nitrogen and phosphate acquisition, cell division (ftsHZ), heat shock response (dnaK, groEL), and uptake of inorganic carbon (rbc, bicA). Genes transcribed during nighttime included those involved in phycobilisome protein synthesis and Photosystem I core subunits. Hierarchical clustering and principal component analysis (PCA) showed a tightly clustered group of nighttime expressed genes, whereas daytime transcripts were separated from each other over the 48-h duration. Lack of uniform clustering within the daytime transcripts suggested that the partitioning of gene expression in Microcystis is dependent on both circadian regulation and physicochemical changes within the environment.
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Affiliation(s)
- Emily J. Davenport
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States,Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, Ann Arbor, MI, United States
| | - Michelle J. Neudeck
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States
| | - Paul G. Matson
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States
| | - George S. Bullerjahn
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States,*Correspondence: George S. Bullerjahn,
| | - Timothy W. Davis
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States
| | - Steven W. Wilhelm
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Maddie K. Denney
- Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Lauren E. Krausfeldt
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Joshua M. A. Stough
- Department of Microbiology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Kevin A. Meyer
- Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, Ann Arbor, MI, United States,Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, United States
| | - Gregory J. Dick
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, United States
| | - Thomas H. Johengen
- Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, Ann Arbor, MI, United States
| | - Erika Lindquist
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA, United States
| | - Susannah G. Tringe
- U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA, United States
| | - Robert Michael L. McKay
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, United States,Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada
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19
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Sicora CI, Chiș I, Chiș C, Sicora O. Regulation of PSII function in Cyanothece sp. ATCC 51142 during a light-dark cycle. PHOTOSYNTHESIS RESEARCH 2019; 139:461-473. [PMID: 30357676 DOI: 10.1007/s11120-018-0598-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 10/15/2018] [Indexed: 06/08/2023]
Abstract
Cyanobacteria, as well as green algae and higher plants, have highly conserved photosynthetic machinery. Cyanothece sp. ATCC 51142 is a unicellular, aerobic, diazotrophic cyanobacterium that fixes N2 in the dark. In Cyanothece, the psbA gene family is composed of five members, encoding different isoforms of the D1 protein. A new D1 protein has been postulated in the literature, which blocks PSII during the night and allows the fixation of nitrogen. We present data showing changes in PSII function in cells grown in cycles alternating between 12 h of light and dark, respectively, at Cyanothece sp. ATCC 51142. Cyanothece sp. ATCC 51142 uses intrinsic mechanisms to protect its nitrogenase activity in a two-stage process. In Stage I, immediately after the onset of darkness, the cells lose photosynthetic activity in a reversible process, probably by dissociation of water oxidation complex from photosystem II via a mechanism that does not require de novo protein synthesis. In Stage II, a more severe disruption of photosystem II function occurs is in part protein synthesis dependent and it could be a functional signature of the presence of sentinel D1 in a limited number of reaction centers still active or not yet inactivated by the mechanism described in Stage I. This process of inhibition uses light as a triggering signal for both the inhibition of photosynthetic activity and recovery when light returns. The intrinsic mechanism of photosynthetic inactivation during darkness with the interplay of the two mechanisms requires further studies.
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Affiliation(s)
- Cosmin Ionel Sicora
- Biological Research Center Jibou, 16 Wesselenyi Street, 455200, Jibou, Sălaj, Romania.
| | - Iuliana Chiș
- Biological Research Center Jibou, 16 Wesselenyi Street, 455200, Jibou, Sălaj, Romania
| | - Ciprian Chiș
- Biological Research Center Jibou, 16 Wesselenyi Street, 455200, Jibou, Sălaj, Romania
| | - Oana Sicora
- Biological Research Center Jibou, 16 Wesselenyi Street, 455200, Jibou, Sălaj, Romania
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