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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.
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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
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2
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Coale TH, Loconte V, Turk-Kubo KA, Vanslembrouck B, Mak WKE, Cheung S, Ekman A, Chen JH, Hagino K, Takano Y, Nishimura T, Adachi M, Le Gros M, Larabell C, Zehr JP. Nitrogen-fixing organelle in a marine alga. Science 2024; 384:217-222. [PMID: 38603509 DOI: 10.1126/science.adk1075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 02/22/2024] [Indexed: 04/13/2024]
Abstract
Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Biological nitrogen fixation, the reduction of abundant atmospheric nitrogen gas (N2) to biologically available ammonia, is a key metabolic process performed exclusively by prokaryotes. Candidatus Atelocyanobacterium thalassa, or UCYN-A, is a metabolically streamlined N2-fixing cyanobacterium previously reported to be an endosymbiont of a marine unicellular alga. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N2-fixing organelle, or "nitroplast."
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Affiliation(s)
- Tyler H Coale
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
| | - Valentina Loconte
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
| | - Bieke Vanslembrouck
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Shunyan Cheung
- Institute of Marine Biology and Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, Taiwan
| | - Axel Ekman
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
| | - Jian-Hua Chen
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Kyoko Hagino
- Marine Core Research Institute, Kochi University, Nankoku, Kochi, Japan
| | - Yoshihito Takano
- Marine Core Research Institute, Kochi University, Nankoku, Kochi, Japan
| | - Tomohiro Nishimura
- Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Hatsukaichi, Hiroshima, Japan
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Nankoku, Kochi, Japan
| | - Masao Adachi
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Nankoku, Kochi, Japan
| | - Mark Le Gros
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Carolyn Larabell
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
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Haydon TD, Matthews JL, Seymour JR, Raina JB, Seymour JE, Chartrand K, Camp EF, Suggett DJ. Metabolomic signatures of corals thriving across extreme reef habitats reveal strategies of heat stress tolerance. Proc Biol Sci 2023; 290:20221877. [PMID: 36750192 PMCID: PMC9904954 DOI: 10.1098/rspb.2022.1877] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 01/11/2023] [Indexed: 02/09/2023] Open
Abstract
Anthropogenic stressors continue to escalate worldwide, driving unprecedented declines in reef environmental conditions and coral health. One approach to better understand how corals can function in the future is to examine coral populations that thrive within present day naturally extreme habitats. We applied untargeted metabolomics (gas chromatography-mass spectrometry (GC-MS)) to contrast metabolite profiles of Pocillopora acuta colonies from hot, acidic and deoxygenated mangrove environments versus those from adjacent reefs. Under ambient temperatures, P. acuta predominantly associated with endosymbionts of the genera Cladocopium (reef) or Durusdinium (mangrove), exhibiting elevated metabolism in mangrove through energy-generating and biosynthesis pathways compared to reef populations. Under transient heat stress, P. acuta endosymbiont associations were unchanged. Reef corals bleached and exhibited extensive shifts in symbiont metabolic profiles (whereas host metabolite profiles were unchanged). By contrast, mangrove populations did not bleach and solely the host metabolite profiles were altered, including cellular responses in inter-partner signalling, antioxidant capacity and energy storage. Thus mangrove P. acuta populations resist periodically high-temperature exposure via association with thermally tolerant endosymbionts coupled with host metabolic plasticity. Our findings highlight specific metabolites that may be biomarkers of heat tolerance, providing novel insight into adaptive coral resilience to elevated temperatures.
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Affiliation(s)
- Trent D. Haydon
- Center for Genomics and Systems Biology, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Jennifer L. Matthews
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Justin R. Seymour
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Jean-Baptiste Raina
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Jamie E. Seymour
- Division of Tropical Health and Medicine, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD 4811, Australia
| | - Kathryn Chartrand
- Centre for tropical Water and Aquatic Ecosystem Research, James Cook University, Cairns, QLD 4811, Australia
| | - Emma F. Camp
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - David J. Suggett
- Faculty of Science, Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
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Salas K, Cabello AM, Turk-Kubo KA, Zehr JP, Cornejo-Castillo FM. Primer design for the amplification of the ammonium transporter genes from the uncultured haptophyte algal species symbiotic with the marine nitrogen-fixing cyanobacterium UCYN-A1. Front Microbiol 2023; 14:1130695. [PMID: 37138636 PMCID: PMC10150950 DOI: 10.3389/fmicb.2023.1130695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 03/21/2023] [Indexed: 05/05/2023] Open
Abstract
The multiple symbiotic partnerships between closely related species of the haptophyte algae Braarudosphaera bigelowii and the nitrogen-fixing cyanobacteria Candidatus Atelocyanobacterium thalassa (UCYN-A) contribute importantly to the nitrogen and carbon cycles in vast areas of the ocean. The diversity of the eukaryotic 18S rDNA phylogenetic gene marker has helped to identify some of these symbiotic haptophyte species, yet we still lack a genetic marker to assess its diversity at a finer scale. One of such genes is the ammonium transporter (amt) gene, which encodes the protein that might be involved in the uptake of ammonium from UCYN-A in these symbiotic haptophytes. Here, we designed three specific PCR primer sets targeting the amt gene of the haptophyte species (A1-Host) symbiotic with the open ocean UCYN-A1 sublineage, and tested them in samples collected from open ocean and near-shore environments. Regardless of the primer pair used at Station ALOHA, which is where UCYN-A1 is the pre-dominant UCYN-A sublineage, the most abundant amt amplicon sequence variant (ASV) was taxonomically classified as A1-Host. In addition, two out of the three PCR primer sets revealed the existence of closely-related divergent haptophyte amt ASVs (>95% nucleotide identity). These divergent amt ASVs had higher relative abundances than the haptophyte typically associated with UCYN-A1 in the Bering Sea, or co-occurred with the previously identified A1-Host in the Coral Sea, suggesting the presence of new diversity of closely-related A1-Hosts in polar and temperate waters. Therefore, our study reveals an overlooked diversity of haptophytes species with distinct biogeographic distributions partnering with UCYN-A, and provides new primers that will help to gain new knowledge of the UCYN-A/haptophyte symbiosis.
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Affiliation(s)
- Krystal Salas
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Ana M. Cabello
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
- Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, IEO-CSIC, Málaga, Spain
| | - Kendra A. Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
- *Correspondence: Jonathan P. Zehr,
| | - Francisco M. Cornejo-Castillo
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
- Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM-CSIC), Barcelona, Spain
- Francisco M. Cornejo-Castillo,
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Gao M, Armin G, Inomura K. Low-Ammonium Environment Increases the Nutrient Exchange between Diatom-Diazotroph Association Cells and Facilitates Photosynthesis and N 2 Fixation-a Mechanistic Modeling Analysis. Cells 2022; 11:cells11182911. [PMID: 36139486 PMCID: PMC9497195 DOI: 10.3390/cells11182911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/09/2022] [Accepted: 09/13/2022] [Indexed: 11/16/2022] Open
Abstract
Diatom–diazotroph associations (DDAs) are one of the most important symbiotic dinitrogen (N2) fixing groups in the oligotrophic ocean. Despite their capability to fix N2, ammonium (NH4+) remains a key nitrogen (N) source for DDAs, and the effect of NH4+ on their metabolism remains elusive. Here, we developed a coarse-grained, cellular model of the DDA with NH4+ uptake and quantified how the level of extracellular NH4+ influences metabolism and nutrient exchange within the symbiosis. The model shows that, under a fixed growth rate, an increased NH4+ concentration may lower the required level of N2 fixation and photosynthesis, and decrease carbon (C) and N exchange. A low-NH4+ environment leads to more C and N in nutrient exchange and more fixed N2 to support a higher growth rate. With higher growth rates, nutrient exchange and metabolism increased. Our study shows a strong effect of NH4+ on metabolic processes within DDAs, and thus highlights the importance of in situ measurement of NH4+ concentrations.
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Affiliation(s)
- Meng Gao
- Correspondence: ; Tel.: +1-401-771-5757
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Calhoun S, Kamel B, Bell TA, Kruse CP, Riley R, Singan V, Kunde Y, Gleasner CD, Chovatia M, Sandor L, Daum C, Treen D, Bowen BP, Louie KB, Northen TR, Starkenburg SR, Grigoriev IV. Multi-omics profiling of the cold tolerant Monoraphidium minutum 26B-AM in response to abiotic stress. ALGAL RES 2022. [DOI: 10.1016/j.algal.2022.102794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Fan X, Zhou J, Xia J, Yan X. Genome-Scale Metabolic Model's multi-objective solving algorithm based on the inflexion point of Pareto front including maximum energy utilization and its application in A.niger DS03043. Biotechnol Bioeng 2022; 119:1539-1555. [PMID: 35274299 DOI: 10.1002/bit.28078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/20/2022] [Accepted: 03/03/2022] [Indexed: 11/06/2022]
Abstract
The solution of genome-scale metabolic model (GSMM) directly affects the simulation accuracy of the metabolic process in digital cells. Single-objective optimization methods, such as Flux Balance Analysis (FBA) which is widely used in solving GSMM, have limitations when simulating actual biological processes, which leads to unrealistic results due to other biological constraints being ignored. A novel multi-objective Differential Evolution algorithm based on general FBA (i.e., DEFBA) is hence proposed to solve GSMM. First, in accordance with to the assumption that cells minimize resource consumption and maximize resource utilization, the maximum specific growth rate and the minimum cellular production rate of ATP, NADPH, and NADH are defined as the multi-objective functions of DEFBA. Second, FBA is used to produce the initial individuals of DEFBA by changing the upper bound of biomass reaction in GSMM. Third, mutation and selection operations help in generating new individuals in the solution space to search the Pareto front. Finally, the optimal solution is selected by analyzing the inflexion point of the Pareto front. In DEFBA, multi-objective technology and optimal solution judging technology can introduce the biological constraints into the GSMM solving method, such that the solution can be more consistent with the essential biological mechanism. DEFBA is applied to solve Aspergillus niger's GSMM. The improved results show that DEFBA can be an effective general solving algorithm for GSMM. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Xingcun Fan
- Key Laboratory of Smart Manufacturing in Energy Chemical Process, Ministry of Education, East China University of Science and Technology, Shanghai, 200237, P. R. China
| | - Jingru Zhou
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China
| | - Jianye Xia
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China
| | - Xuefeng Yan
- Key Laboratory of Smart Manufacturing in Energy Chemical Process, Ministry of Education, East China University of Science and Technology, Shanghai, 200237, P. R. China
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Metabolic Model of the Nitrogen-Fixing Obligate Aerobe Azotobacter vinelandii Predicts Its Adaptation to Oxygen Concentration and Metal Availability. mBio 2021; 12:e0259321. [PMID: 34903060 PMCID: PMC8686835 DOI: 10.1128/mbio.02593-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is considerable interest in promoting biological nitrogen fixation (BNF) as a mechanism to reduce the inputs of nitrogenous fertilizers in agriculture, but considerable fundamental knowledge gaps still need to be addressed. BNF is catalyzed by nitrogenase, which requires a large input of energy in the form of ATP and low potential electrons. Diazotrophs that respire aerobically have an advantage in meeting the ATP demands of BNF but face challenges in protecting nitrogenase from inactivation by oxygen. Here, we constructed a genome-scale metabolic model of the nitrogen-fixing bacterium Azotobacter vinelandii, which uses a complex respiratory protection mechanism to consume oxygen at a high rate to keep intracellular conditions microaerobic. Our model accurately predicts growth rate under high oxygen and substrate concentrations, consistent with a large electron flux directed to the respiratory protection mechanism. While a partially decoupled electron transport chain compensates for some of the energy imbalance under high-oxygen conditions, it does not account for all substrate intake, leading to increased maintenance rates. Interestingly, the respiratory protection mechanism is required for accurate predictions even when ammonia is supplemented during growth, suggesting that the respiratory protection mechanism might be a core principle of metabolism and not just used for nitrogenase protection. We have also shown that rearrangement of flux through the electron transport system allows A. vinelandii to adapt to different oxygen concentrations, metal availability, and genetic disruption, which cause an ammonia excretion phenotype. Accurately determining the energy balance in an aerobic nitrogen-fixing metabolic model is required for future engineering approaches.
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Landa M, Turk-Kubo KA, Cornejo-Castillo FM, Henke BA, Zehr JP. Critical Role of Light in the Growth and Activity of the Marine N 2-Fixing UCYN-A Symbiosis. Front Microbiol 2021; 12:666739. [PMID: 34025621 PMCID: PMC8139342 DOI: 10.3389/fmicb.2021.666739] [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: 02/10/2021] [Accepted: 04/08/2021] [Indexed: 11/27/2022] Open
Abstract
The unicellular N2-fixing cyanobacteria UCYN-A live in symbiosis with haptophytes in the Braarudosphaera bigelowii lineage. Maintaining N2-fixing symbioses between two unicellular partners requires tight coordination of multiple biological processes including cell growth and division and, in the case of the UCYN-A symbiosis, N2 fixation of the symbiont and photosynthesis of the host. In this system, it is thought that the host photosynthesis supports the high energetic cost of N2 fixation, and both processes occur during the light period. However, information on this coordination is very limited and difficult to obtain because the UCYN-A symbiosis has yet to be available in culture. Natural populations containing the UCYN-A2 symbiosis were manipulated to explore the effects of alterations of regular light and dark periods and inhibition of host photosynthesis on N2 fixation (single cell N2 fixation rates), nifH gene transcription, and UCYN-A2 cell division (fluorescent in situ hybridization and nifH gene abundances). The results showed that the light period is critical for maintenance of regular patterns of gene expression, N2 fixation and symbiont replication and cell division. This study suggests a crucial role for the host as a producer of fixed carbon, rather than light itself, in the regulation and implementation of these cellular processes in UCYN-A.
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Affiliation(s)
- Marine Landa
- Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, United States
| | | | - Britt A Henke
- Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, United States
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