1
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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2
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Cornejo-Castillo FM, Inomura K, Zehr JP, Follows MJ. Metabolic trade-offs constrain the cell size ratio in a nitrogen-fixing symbiosis. Cell 2024; 187:1762-1768.e9. [PMID: 38471501 DOI: 10.1016/j.cell.2024.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 10/06/2023] [Accepted: 02/14/2024] [Indexed: 03/14/2024]
Abstract
Biological dinitrogen (N2) fixation is a key metabolic process exclusively performed by prokaryotes, some of which are symbiotic with eukaryotes. Species of the marine haptophyte algae Braarudosphaera bigelowii harbor the N2-fixing endosymbiotic cyanobacteria UCYN-A, which might be evolving organelle-like characteristics. We found that the size ratio between UCYN-A and their hosts is strikingly conserved across sublineages/species, which is consistent with the size relationships of organelles in this symbiosis and other species. Metabolic modeling showed that this size relationship maximizes the coordinated growth rate based on trade-offs between resource acquisition and exchange. Our findings show that the size relationships of N2-fixing endosymbionts and organelles in unicellular eukaryotes are constrained by predictable metabolic underpinnings and that UCYN-A is, in many regards, functioning like a hypothetical N2-fixing organelle (or nitroplast).
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Affiliation(s)
- Francisco M Cornejo-Castillo
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar, ICM-CSIC, Barcelona 08003, Spain; Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.
| | - Keisuke Inomura
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA.
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Michael J Follows
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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3
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Kramer BJ, Turk-Kubo K, Zehr JP, Gobler CJ. Intensification of harmful cyanobacterial blooms in a eutrophic, temperate lake caused by nitrogen, temperature, and CO 2. Sci Total Environ 2024; 915:169885. [PMID: 38190910 DOI: 10.1016/j.scitotenv.2024.169885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 01/01/2024] [Accepted: 01/01/2024] [Indexed: 01/10/2024]
Abstract
Warmer temperatures can significantly increase the intensity of cyanobacterial harmful algal blooms (CHABs) in eutrophic freshwater ecosystems. However, few studies have examined the effects of CO2 enrichment in tandem with elevated temperature and/or nutrients on cyanobacterial taxa in freshwater ecosystems. Here, we observed changes in the biomass of cyanobacteria, nutrients, pH, and carbonate chemistry over a two-year period in a shallow, eutrophic freshwater lake and performed experiments to examine the effects and co-effects of CO2, temperature, and nutrient enrichment on cyanobacterial and N2-fixing (diazotrophic) communities assessed via high throughput sequencing of the 16S rRNA and nifH genes, respectively. During both years, there were significant CHABs (50-500 μg cyanobacterial chlorophyll-a L-1) and lake CO2 levels were undersaturated (≤300 μatm pCO2). NH4+ significantly increased the net growth rates of cyanobacteria as well as the biomass of the diazotrophic cyanobacterial order Nostocales under elevated and ambient CO2 conditions. In a fall experiment, the N2 fixation rates of Nostocales were significantly higher when populations were enriched with CO2 and P, relative to CO2-enriched populations that were not amended with P. During a summer experiment, N2 fixation rates increased significantly under N and CO2 - enriched conditions relative to N-enriched and ambient CO2 conditions. Nostocales dominated the diazotrophic communities of both experiments, achieving the highest relative abundance under CO2-enriched conditions when N was added in the first experiment and when CO2 and temperature were elevated in the second experiment, when N2 fixation rates also increased significantly. Collectively, this study indicates that N promotes cyanobacterial blooms including those formed by Dolichospermum and that the biomass and N2 fixation rates of diazotrophic cyanobacterial taxa may benefit from enhanced CO2 levels in eutrophic lakes.
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Affiliation(s)
- Benjamin J Kramer
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States
| | - Kendra Turk-Kubo
- Oceans Sciences Department, University of California at Santa Cruz, CA, United States
| | - Jonathan P Zehr
- Oceans Sciences Department, University of California at Santa Cruz, CA, United States
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States.
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4
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Moore LR, Caspi R, Campbell DA, Casey JR, Crevecoeur S, Lea-Smith DJ, Long B, Omar NM, Paley SM, Schmelling NM, Torrado A, Zehr JP, Karp PD. CyanoCyc cyanobacterial web portal. Front Microbiol 2024; 15:1340413. [PMID: 38357349 PMCID: PMC10864581 DOI: 10.3389/fmicb.2024.1340413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/11/2024] [Indexed: 02/16/2024] Open
Abstract
CyanoCyc is a web portal that integrates an exceptionally rich database collection of information about cyanobacterial genomes with an extensive suite of bioinformatics tools. It was developed to address the needs of the cyanobacterial research and biotechnology communities. The 277 annotated cyanobacterial genomes currently in CyanoCyc are supplemented with computational inferences including predicted metabolic pathways, operons, protein complexes, and orthologs; and with data imported from external databases, such as protein features and Gene Ontology (GO) terms imported from UniProt. Five of the genome databases have undergone manual curation with input from more than a dozen cyanobacteria experts to correct errors and integrate information from more than 1,765 published articles. CyanoCyc has bioinformatics tools that encompass genome, metabolic pathway and regulatory informatics; omics data analysis; and comparative analyses, including visualizations of multiple genomes aligned at orthologous genes, and comparisons of metabolic networks for multiple organisms. CyanoCyc is a high-quality, reliable knowledgebase that accelerates scientists' work by enabling users to quickly find accurate information using its powerful set of search tools, to understand gene function through expert mini-reviews with citations, to acquire information quickly using its interactive visualization tools, and to inform better decision-making for fundamental and applied research.
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Affiliation(s)
| | - Ron Caspi
- SRI International, Menlo Park, CA, United States
| | | | - John R. Casey
- Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, Livermore, CA, United States
| | - Sophie Crevecoeur
- Watershed Hydrology and Ecology Research Division, Environment and Climate Change Canada, Burlington, ON, Canada
| | - David J. Lea-Smith
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Bin Long
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, United States
| | | | | | | | - Alejandro Torrado
- Institute of Plant Biochemistry and Photosynthesis, University of Seville and Spanish National Research Council, Sevilla, Spain
| | - Jonathan P. Zehr
- Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, United States
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5
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Turk-Kubo KA, Gradoville MR, Cheung S, Cornejo-Castillo FM, Harding KJ, Morando M, Mills M, Zehr JP. Non-cyanobacterial diazotrophs: global diversity, distribution, ecophysiology, and activity in marine waters. FEMS Microbiol Rev 2023; 47:fuac046. [PMID: 36416813 PMCID: PMC10719068 DOI: 10.1093/femsre/fuac046] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/15/2022] [Accepted: 11/17/2022] [Indexed: 12/17/2023] Open
Abstract
Biological dinitrogen (N2) fixation supplies nitrogen to the oceans, supporting primary productivity, and is carried out by some bacteria and archaea referred to as diazotrophs. Cyanobacteria are conventionally considered to be the major contributors to marine N2 fixation, but non-cyanobacterial diazotrophs (NCDs) have been shown to be distributed throughout ocean ecosystems. However, the biogeochemical significance of marine NCDs has not been demonstrated. This review synthesizes multiple datasets, drawing from cultivation-independent molecular techniques and data from extensive oceanic expeditions, to provide a comprehensive view into the diversity, biogeography, ecophysiology, and activity of marine NCDs. A NCD nifH gene catalog was compiled containing sequences from both PCR-based and PCR-free methods, identifying taxa for future studies. NCD abundances from a novel database of NCD nifH-based abundances were colocalized with environmental data, unveiling distinct distributions and environmental drivers of individual taxa. Mechanisms that NCDs may use to fuel and regulate N2 fixation in response to oxygen and fixed nitrogen availability are discussed, based on a metabolic analysis of recently available Tara Oceans expedition data. The integration of multiple datasets provides a new perspective that enhances understanding of the biology, ecology, and biogeography of marine NCDs and provides tools and directions for future research.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Mary R Gradoville
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Columbia River Inter-Tribal Fish Commission, Portland, OR, United States
| | - Shunyan Cheung
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Francisco M Cornejo-Castillo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM-CSIC), Pg. Marítim Barceloneta, 37-49 08003 Barcelona, Spain
| | - Katie J Harding
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Marine Biology Research Division, Scripps Institute of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - Michael Morando
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Matthew Mills
- Department of Earth System Science, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
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6
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Zehr JP, Capone DG. Unsolved mysteries in marine nitrogen fixation. Trends Microbiol 2023:S0966-842X(23)00235-4. [PMID: 37658011 DOI: 10.1016/j.tim.2023.08.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [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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7
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Turk-Kubo KA, Loconte V, Vanslembrouck B, Mak WKE, Ekman A, Chen JH, Takano Y, Horiguchi T, Nishimura T, Adachi M, Gros ML, Hagino K, Zehr JP, Larabell C. Soft X-ray Tomography Enables New Insights into the Coordinated Division of Organelle-like Symbiont in a Globally Distributed Unicellular Marine Haptophyte Alga. Microsc Microanal 2023; 29:1165. [PMID: 37613509 DOI: 10.1093/micmic/ozad067.596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, California, United States
| | - Valentina Loconte
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
| | - Bieke Vanslembrouck
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
| | - Wing Kwan Esther Mak
- Ocean Sciences Department, University of California, Santa Cruz, California, United States
| | - Axel Ekman
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
| | - Jian-Hua Chen
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
| | - Yoshihito Takano
- Center for Advanced Marine Core Research, Kochi University, Kochi, Japan
| | - Takeo Horiguchi
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Kochi, Japan
| | - Tomohiro Nishimura
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Kochi, Japan
| | - Masao Adachi
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Kochi, Japan
| | - Mark Le Gros
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
| | - Kyoko Hagino
- Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, California, United States
| | - Carolyn Larabell
- Department of Anatomy, School of Medicine, University of California San Francisco, San Francisco, California, United States
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
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8
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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9
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Muñoz-Marín MDC, Magasin JD, Zehr JP. Open ocean and coastal strains of the N2-fixing cyanobacterium UCYN-A have distinct transcriptomes. PLoS One 2023; 18:e0272674. [PMID: 37130101 PMCID: PMC10153697 DOI: 10.1371/journal.pone.0272674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 02/18/2023] [Indexed: 05/03/2023] Open
Abstract
Decades of research on marine N2 fixation focused on Trichodesmium, which are generally free-living cyanobacteria, but in recent years the endosymbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) has received increasing attention. However, few studies have shed light on the influence of the host versus the habitat on UCYN-A N2 fixation and overall metabolism. Here we compared transcriptomes from natural populations of UCYN-A from oligotrophic open-ocean versus nutrient-rich coastal waters, using a microarray that targets the full genomes of UCYN-A1 and UCYN-A2 and known genes for UCYN-A3. We found that UCYN-A2, usually regarded as adapted to coastal environments, was transcriptionally very active in the open ocean and appeared to be less impacted by habitat change than UCYN-A1. Moreover, for genes with 24 h periodic expression we observed strong but inverse correlations among UCYN-A1, A2, and A3 to oxygen and chlorophyll, which suggests distinct host-symbiont relationships. Across habitats and sublineages, genes for N2 fixation and energy production had high transcript levels, and, intriguingly, were among the minority of genes that kept the same schedule of diel expression. This might indicate different regulatory mechanisms for genes that are critical to the symbiosis for the exchange of nitrogen for carbon from the host. Our results underscore the importance of N2 fixation in UCYN-A symbioses across habitats, with consequences for community interactions and global biogeochemical cycles.
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Affiliation(s)
- María Del Carmen Muñoz-Marín
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario, Universidad de Córdoba, Córdoba, Spain
| | - Jonathan D Magasin
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
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10
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Gradoville MR, Dugenne M, Hynes AM, Zehr JP, White AE. Empirical relationship between nifH gene abundance and diazotroph cell concentration in the North Pacific Subtropical Gyre. J Phycol 2022; 58:829-833. [PMID: 36266252 DOI: 10.1111/jpy.13289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/24/2022] [Indexed: 06/16/2023]
Abstract
Cyanobacterial N2 -fixing microorganisms (diazotrophs) play a critical role in nitrogen and carbon cycling in the oceans; hence, accurate measurements of diazotroph abundance are imperative for understanding ocean biogeochemistry. Marine diazotroph abundances are often assessed using qPCR of the nifH gene, a sensitive, taxa-specific, and time/cost-efficient method. However, the validity of nifH abundance as a proxy for cell concentration has recently been questioned. Here, we compare nifH gene abundances to cell counts for four diazotroph taxa (Trichodesmium, Crocosphaera, Richelia, and Calothrix) on two cruises to the North Pacific Subtropical Gyre, one of the largest habitats for marine diazotrophs. nifH:cell relationships were strong and significant for Crocosphaera, Richelia, and Calothrix (nifH:cell 1.51-2.58; R2 = 0.89-0.96) but were not significant for Trichodesmium, despite previous studies reporting significant nifH:cell relationships for this organism. Limited available data suggest that empirical nifH:cell can vary among studies but that relationships are usually significantly linear and >1:1. Our study indicates that nifH gene abundance, while not a direct measure of cells, is a useful quantitative proxy for diazotroph abundance.
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Affiliation(s)
- Mary R Gradoville
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, California, 95064, USA
| | - Mathilde Dugenne
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, Hawaii, 96822, USA
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mānoa, Honolulu, Hawaii, 96822, USA
| | - Annette M Hynes
- School of Oceanography, University of Washington, Seattle, Washington, 98195, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, California, 95064, USA
| | - Angelicque E White
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, Hawaii, 96822, USA
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mānoa, Honolulu, Hawaii, 96822, USA
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11
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Harding KJ, Turk-Kubo KA, Mak EWK, Weber PK, Mayali X, Zehr JP. Cell-specific measurements show nitrogen fixation by particle-attached putative non-cyanobacterial diazotrophs in the North Pacific Subtropical Gyre. Nat Commun 2022; 13:6979. [PMID: 36379938 PMCID: PMC9666432 DOI: 10.1038/s41467-022-34585-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 10/31/2022] [Indexed: 11/16/2022] Open
Abstract
Biological nitrogen fixation is a major important source of nitrogen for low-nutrient surface oceanic waters. Nitrogen-fixing (diazotrophic) cyanobacteria are believed to be the primary contributors to this process, but the contribution of non-cyanobacterial diazotrophic organisms in oxygenated surface water, while hypothesized to be important, has yet to be demonstrated. In this study, we used simultaneous 15N-dinitrogen and 13C-bicarbonate incubations combined with nanoscale secondary ion mass spectrometry analysis to screen tens of thousands of mostly particle-associated, cell-like regions of interest collected from the North Pacific Subtropical Gyre. These dual isotope incubations allow us to distinguish between non-cyanobacterial and cyanobacterial nitrogen-fixing microorganisms and to measure putative cell-specific nitrogen fixation rates. With this approach, we detect nitrogen fixation by putative non-cyanobacterial diazotrophs in the oxygenated surface ocean, which are associated with organic-rich particles (<210 µm size fraction) at two out of seven locations sampled. When present, up to 4.1% of the analyzed particles contain at least one active putative non-cyanobacterial diazotroph. The putative non-cyanobacterial diazotroph nitrogen fixation rates (0.76 ± 1.60 fmol N cell-1 d-1) suggest that these organisms are capable of fixing dinitrogen in oxygenated surface water, at least when attached to particles, and may contribute to oceanic nitrogen fixation.
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Affiliation(s)
- Katie J Harding
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
| | | | - Peter K Weber
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Xavier Mayali
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA.
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA.
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12
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Dextro RB, Delbaje E, Cotta SR, Zehr JP, Fiore MF. Trends in Free-access Genomic Data Accelerate Advances in Cyanobacteria Taxonomy. J Phycol 2021; 57:1392-1402. [PMID: 34291461 DOI: 10.1111/jpy.13200] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 07/16/2021] [Indexed: 06/13/2023]
Abstract
Free access databases of DNA sequences containing microbial genetic information have changed the way scientists look at the microbial world. Currently, the NCBI database includes about 516 distinct search results for Cyanobacterial genomes distributed in a taxonomy based on a polyphasic approach. While their classification and taxonomic relationships are widely used as is, recent proposals to alter their grouping include further exploring the relationship between Cyanobacteria and Melainabacteria. Nowadays, most cyanobacteria still are named under the Botanical Code; however, there is a proposal made by the Genome Taxonomy Database (GTDB) to harmonize cyanobacteria nomenclature with the other bacteria, an initiative to standardize microbial taxonomy based on genome phylogeny, in order to contribute to an overall better phylogenetic resolution of microbiota. Furthermore, the assembly level of the genomes and their geographical origin demonstrates some trends of cyanobacteria genomics on the scientific community, such as low availability of complete genomes and underexplored sampling locations. By describing how available cyanobacterial genomes from free-access databases fit within different taxonomic classifications, this mini-review provides a holistic view of the current knowledge of cyanobacteria and indicates some steps towards improving our efforts to create a more cohesive and inclusive classifying system, which can be greatly improved by using large-scale sequencing and metagenomic techniques.
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Affiliation(s)
- Rafael B Dextro
- Center for Nuclear Energy in Agriculture, University of São Paulo, Avenida Centenário 303, 13416-000, Piracicaba, SP, Brazil
| | - Endrews Delbaje
- Center for Nuclear Energy in Agriculture, University of São Paulo, Avenida Centenário 303, 13416-000, Piracicaba, SP, Brazil
| | - Simone R Cotta
- Center for Nuclear Energy in Agriculture, University of São Paulo, Avenida Centenário 303, 13416-000, Piracicaba, SP, Brazil
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
| | - Marli F Fiore
- Center for Nuclear Energy in Agriculture, University of São Paulo, Avenida Centenário 303, 13416-000, Piracicaba, SP, Brazil
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13
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Turk-Kubo KA, Mills MM, Arrigo KR, van Dijken G, Henke BA, Stewart B, Wilson ST, Zehr JP. UCYN-A/haptophyte symbioses dominate N 2 fixation in the Southern California Current System. ISME Commun 2021; 1:42. [PMID: 36740625 PMCID: PMC9723760 DOI: 10.1038/s43705-021-00039-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 02/07/2023]
Abstract
The availability of fixed nitrogen (N) is an important factor limiting biological productivity in the oceans. In coastal waters, high dissolved inorganic N concentrations were historically thought to inhibit dinitrogen (N2) fixation, however, recent N2 fixation measurements and the presence of the N2-fixing UCYN-A/haptophyte symbiosis in nearshore waters challenge this paradigm. We characterized the contribution of UCYN-A symbioses to nearshore N2 fixation in the Southern California Current System (SCCS) by measuring bulk community and single-cell N2 fixation rates, as well as diazotroph community composition and abundance. UCYN-A1 and UCYN-A2 symbioses dominated diazotroph communities throughout the region during upwelling and oceanic seasons. Bulk N2 fixation was detected in most surface samples, with rates up to 23.0 ± 3.8 nmol N l-1 d-1, and was often detected at the deep chlorophyll maximum in the presence of nitrate (>1 µM). UCYN-A2 symbiosis N2 fixation rates were higher (151.1 ± 112.7 fmol N cell-1 d-1) than the UCYN-A1 symbiosis (6.6 ± 8.8 fmol N cell-1 d-1). N2 fixation by the UCYN-A1 symbiosis accounted for a majority of the measured bulk rates at two offshore stations, while the UCYN-A2 symbiosis was an important contributor in three nearshore stations. This report of active UCYN-A symbioses and broad mesoscale distribution patterns establishes UCYN-A symbioses as the dominant diazotrophs in the SCCS, where heterocyst-forming and unicellular cyanobacteria are less prevalent, and provides evidence that the two dominant UCYN-A sublineages are separate ecotypes.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA.
| | - Matthew M Mills
- Earth System Science, Stanford University, Stanford, CA, USA
| | - Kevin R Arrigo
- Earth System Science, Stanford University, Stanford, CA, USA
| | - Gert van Dijken
- Earth System Science, Stanford University, Stanford, CA, USA
| | - Britt A Henke
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA
| | - Brittany Stewart
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Samuel T Wilson
- Center for Microbial Oceanography: Research and Education, University of Hawai'i at Manoa, Honolulu, HI, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA
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14
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Gradoville MR, Cabello AM, Wilson ST, Turk-Kubo KA, Karl DM, Zehr JP. Light and depth dependency of nitrogen fixation by the non-photosynthetic, symbiotic cyanobacterium UCYN-A. Environ Microbiol 2021; 23:4518-4531. [PMID: 34227720 PMCID: PMC9291983 DOI: 10.1111/1462-2920.15645] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/28/2022]
Abstract
The symbiotic cyanobacterium UCYN‐A is one of the most globally abundant marine dinitrogen (N2)‐fixers, but cultures have not been available and its biology and ecology are poorly understood. We used cultivation‐independent approaches to investigate how UCYN‐A single‐cell N2 fixation rates (NFRs) and nifH gene expression vary as a function of depth and photoperiod. Twelve‐hour day/night incubations showed that UCYN‐A only fixed N2 during the day. Experiments conducted using in situ arrays showed a light‐dependence of NFRs by the UCYN‐A symbiosis, with the highest rates in surface waters (5–45 m) and lower rates at depth (≥ 75 m). Analysis of NFRs versus in situ light intensity yielded a light saturation parameter (Ik) for UCYN‐A of 44 μmol quanta m−2 s−1. This is low compared with other marine diazotrophs, suggesting an ecological advantage for the UCYN‐A symbiosis under low‐light conditions. In contrast to cell‐specific NFRs, nifH gene‐specific expression levels did not vary with depth, indicating that light regulates N2 fixation by UCYN‐A through processes other than transcription, likely including host–symbiont interactions. These results offer new insights into the physiology of the UCYN‐A symbiosis in the subtropical North Pacific Ocean and provide clues to the environmental drivers of its global distributions.
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Affiliation(s)
- Mary R Gradoville
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Ana M Cabello
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA.,Centro Oceanográfico de Málaga, Instituto Español de Oceanografía, Fuengirola, Málaga, Spain
| | - Samuel T Wilson
- Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Kendra A Turk-Kubo
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - David M Karl
- Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
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15
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Cheung S, Zehr JP, Xia X, Tsurumoto C, Endo H, Nakaoka SI, Mak W, Suzuki K, Liu H. Gamma4: a genetically versatile Gammaproteobacterial nifH phylotype that is widely distributed in the North Pacific Ocean. Environ Microbiol 2021; 23:4246-4259. [PMID: 34046993 DOI: 10.1111/1462-2920.15604] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 05/15/2021] [Accepted: 05/16/2021] [Indexed: 11/30/2022]
Abstract
Despite the increasing reports of non-cyanobacterial diazotrophs (NCDs) in pelagic waters, only one NCD (GammaA) has been relatively well described, whose genome and physiology are still unclear. Here we present a comprehensive analysis of the biogeography and ecophysiology of a widely distributed NCD, Gamma4. Gamma4 was the most abundant Gammaproteobacterial NCD along transects across the subtropical North Pacific. Using quantitative PCR, Gamma4 was detectable throughout the surface waters of North Pacific (7°N-55°N, 138°E-80°W), whereas GammaA was detected at <2/3 of the stations. Gamma4 was abundant during autumn-winter and positively correlated with chlorophyll a, while GammaA thrived during spring-summer and was positively correlated with temperature. Environmental clones affiliated with Gamma4 were widely detected in pelagic waters, oxygen minimum zones and even dinoflagellate microbiomes. By analysing the metabolic potential of a genome of Gamma4 reconstructed from the Tara Oceans dataset, we suggest that Gamma4 is a versatile heterotrophic NCD equipped with multiple strategies in scavenging phosphate (and iron) and for respiratory protection of nitrogenase. The transcription of nitrogenase genes is putatively regulated by Fnr-NifL-NifA and GlnD-GlnK systems that respond to intracellular oxygen and glutamate concentration. These results provide important implications for the potential life strategies of pelagic NCDs.
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Affiliation(s)
- Shunyan Cheung
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China.,Hong Kong Branch of Southern Marine Science & Engineering Guangdong Laboratory, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Xiaomin Xia
- Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Chihiro Tsurumoto
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Hisashi Endo
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Kyoto, 611-0011, Japan
| | - Shin-Ichiro Nakaoka
- Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Wingkwan Mak
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Koji Suzuki
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan.,Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Hongbin Liu
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China.,Hong Kong Branch of Southern Marine Science & Engineering Guangdong Laboratory, The Hong Kong University of Science and Technology, Hong Kong, China
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16
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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17
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Farnelid H, Turk-Kubo K, Zehr JP. Cell sorting reveals few novel prokaryote and photosynthetic picoeukaryote associations in the oligotrophic ocean. Environ Microbiol 2020; 23:1469-1480. [PMID: 33295132 PMCID: PMC8048811 DOI: 10.1111/1462-2920.15351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 12/04/2020] [Indexed: 11/28/2022]
Abstract
Close associations between single‐celled marine organisms can have a central role in biogeochemical processes and are of great interest for understanding the evolution of organisms. The global significance of such associations raises the question of whether unidentified associations are yet to be discovered. In this study, fluorescence‐activated cell sorted photosynthetic picoeukayote (PPE) populations and single cells were analysed by sequencing of 16S rRNA genes in the oligotrophic North Pacific Subtropical Gyre. Samples were collected during two cruises, spanning depths near the deep chlorophyll maximum, where the abundance of PPEs was highest. The association between the widespread and significant nitrogen (N2)‐fixing cyanobacterium, UCYN‐A and its prymnesiophyte host was prevalent in both population and single‐cell sorts. Several bacterial sequences, affiliating with previously described symbiotic taxa were detected but their detection was rare and not well replicated, precluding identification of novel tightly linked species‐specific associations. Similarly, no enrichment of dominant seawater taxa such as Prochlorococcus, SAR11 or Synechococcus was observed suggesting that these were not systematically ingested by the PPE in this study. The results indicate that apart from the UCYN‐A symbiosis, similar tight species‐specific associations with PPEs are unusual in the oligotrophic ocean.
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Affiliation(s)
- Hanna Farnelid
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA.,Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden
| | - Kendra Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
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18
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Cabello AM, Turk‐Kubo KA, Hayashi K, Jacobs L, Kudela RM, Zehr JP. Unexpected presence of the nitrogen-fixing symbiotic cyanobacterium UCYN-A in Monterey Bay, California. J Phycol 2020; 56:1521-1533. [PMID: 32609873 PMCID: PMC7754506 DOI: 10.1111/jpy.13045] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 06/10/2020] [Indexed: 05/20/2023]
Abstract
In the last decade, the known biogeography of nitrogen fixation in the ocean has been expanded to colder and nitrogen-rich coastal environments. The symbiotic nitrogen-fixing cyanobacteria group A (UCYN-A) has been revealed as one of the most abundant and widespread nitrogen-fixers, and includes several sublineages that live associated with genetically distinct but closely related prymnesiophyte hosts. The UCYN-A1 sublineage is associated with an open ocean picoplanktonic prymnesiophyte, whereas UCYN-A2 is associated with the coastal nanoplanktonic coccolithophore Braarudosphaera bigelowii, suggesting that different sublineages may be adapted to different environments. Here, we study the diversity of nifH genes present at the Santa Cruz Municipal Wharf in the Monterey Bay (MB), California, and report for the first time the presence of multiple UCYN-A sublineages, unexpectedly dominated by the UCYN-A2 sublineage. Sequence and quantitative PCR data over an 8-year time-series (2011-2018) showed a shift toward increasing UCYN-A2 abundances after 2013, and a marked seasonality for this sublineage which was present during summer-fall months, coinciding with the upwelling-relaxation period in the MB. Increased abundances corresponded to positive temperature anomalies in MB, and we discuss the possibility of a benthic life stage of the associated coccolithophore host to explain the seasonal pattern. The dominance of UCYN-A2 in coastal waters of the MB underscores the need to further explore the habitat preference of the different sublineages in order to provide additional support for the hypothesis that UCYN-A1 and UCYN-A2 sublineages are different ecotypes.
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Affiliation(s)
- Ana M. Cabello
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
- Centro Oceanográfico de MálagaInstituto Español de OceanografíaFuengirolaMálaga29001Spain
| | - Kendra A. Turk‐Kubo
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
| | - Kendra Hayashi
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
| | - Lucien Jacobs
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
| | - Raphael M. Kudela
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
| | - Jonathan P. Zehr
- Ocean Sciences DepartmentUniversity of California, Santa CruzSanta CruzCalifornia95064USA
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19
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Abstract
Nitrogen fixation, the reduction of atmospheric dinitrogen gas (N2) to ammonia, is critical for biological productivity but is difficult to study in the vast expanse of the global ocean. Decades of field studies and the infusion of molecular biological, genomic, isotopic, and geochemical modeling approaches have led to new paradigms and questions. The discovery of previously unknown N2-fixing (diazotrophic) microorganisms and unusual physiological adaptations, combined with diagnostic distributions of nutrients and their isotopes as well as measured and modeled biogeographic patterns, have revolutionized our understanding of marine N2 fixation and its role in the global nitrogen cycle. Anthropogenic upper-ocean warming, increased dissolved carbon dioxide, and acidification will affect the distribution and relative importance of specific subgroups of N2 fixers in the sea; these changes have implications for foodwebs and biogeochemical cycles.
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Affiliation(s)
- Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95003, USA
| | - Douglas G. Capone
- Marine and Environmental Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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20
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Abstract
Cyanobacteria are common in symbiotic relationships with diverse multicellular organisms (animals, plants, fungi) in terrestrial environments and with single-celled heterotrophic, mixotrophic, and autotrophic protists in aquatic environments. In the sunlit zones of aquatic environments, diverse cyanobacterial symbioses exist with autotrophic taxa in phytoplankton, including dinoflagellates, diatoms, and haptophytes (prymnesiophytes). Phototrophic unicellular cyanobacteria related to Synechococcus and Prochlorococcus are associated with a number of groups. N2-fixing cyanobacteria are symbiotic with diatoms and haptophytes. Extensive genome reduction is involved in the N2-fixing endosymbionts, most dramatically in the unicellular cyanobacteria associated with haptophytes, which have lost most of the photosynthetic apparatus, the ability to fix C, and the tricarboxylic acid cycle. The mechanisms involved in N2-fixing symbioses may involve more interactions beyond simple exchange of fixed C for N. N2-fixing cyanobacterial symbioses are widespread in the oceans, even more widely distributed than the best-known free-living N2-fixing cyanobacteria, suggesting they may be equally or more important in the global ocean biogeochemical cycle of N.Despite their ubiquitous nature and significance in biogeochemical cycles, cyanobacterium-phytoplankton symbioses remain understudied and poorly understood.
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Affiliation(s)
- Rachel A Foster
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91 Stockholm, Sweden;
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, California 95064, USA;
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21
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Shilova IN, Magasin JD, Mills MM, Robidart JC, Turk-Kubo KA, Zehr JP. Phytoplankton transcriptomic and physiological responses to fixed nitrogen in the California current system. PLoS One 2020; 15:e0231771. [PMID: 32310982 PMCID: PMC7170224 DOI: 10.1371/journal.pone.0231771] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 03/31/2020] [Indexed: 11/18/2022] Open
Abstract
Marine phytoplankton are responsible for approximately half of photosynthesis on Earth. However, their ability to drive ocean productivity depends on critical nutrients, especially bioavailable nitrogen (N) which is scarce over vast areas of the ocean. Phytoplankton differ in their preferences for N substrates as well as uptake efficiencies and minimal N requirements relative to other critical nutrients, including iron (Fe) and phosphorus. In this study, we used the MicroTOOLs high-resolution environmental microarray to examine transcriptomic responses of phytoplankton communities in the California Current System (CCS) transition zone to added urea, ammonium, nitrate, and also Fe in the late summer when N depletion is common. Transcript level changes of photosynthetic, carbon fixation, and nutrient stress genes indicated relief of N limitation in many strains of Prochlorococcus, Synechococcus, and eukaryotic phytoplankton. The transcriptomic responses helped explain shifts in physiological and growth responses observed later. All three phytoplankton groups had increased transcript levels of photosynthesis and/or carbon fixation genes in response to all N substrates. However, only Prochlorococcus had decreased transcript levels of N stress genes and grew substantially, specifically after urea and ammonium additions, suggesting that Prochlorococcus outcompeted other community members in these treatments. Diatom transcript levels of carbon fixation genes increased in response to Fe but not to Fe with N which might have favored phytoplankton that were co-limited by N and Fe. Moreover, transcription patterns of closely related strains indicated variability in N utilization, including nitrate utilization by some high-light adapted Prochlorococcus. Finally, up-regulation of urea transporter genes by both Prochlorococcus and Synechococcus in response to filtered deep water suggested a regulatory mechanism other than classic control via the global N regulator NtcA. This study indicated that co-existing phytoplankton strains experience distinct nutrient stresses in the transition zone of the CCS, an understudied region where oligotrophic and coastal communities naturally mix.
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Affiliation(s)
- Irina N. Shilova
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- * E-mail: (INS); (JPZ)
| | - Jonathan D. Magasin
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Matthew M. Mills
- Department of Earth System Science, Stanford University, Stanford, California, United States of America
| | - Julie C. Robidart
- Ocean Technology and Engineering, National Oceanography Centre, Southampton, England, United Kingdom
| | - Kendra A. Turk-Kubo
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- * E-mail: (INS); (JPZ)
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22
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Garcia‐Pichel F, Zehr JP, Bhattacharya D, Pakrasi HB. What's in a name? The case of cyanobacteria. J Phycol 2020; 56:1-5. [PMID: 31618454 PMCID: PMC7065140 DOI: 10.1111/jpy.12934] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/04/2019] [Indexed: 05/05/2023]
Abstract
A redefinition of the cyanobacterial lineage has been proposed based on phylogenomic analysis of distantly related nonphototrophic lineages. We define Cyanobacteria here as "Organisms in the domain bacteria able to carry out oxygenic photosynthesis with water as an electron donor and to reduce carbon dioxide as a source of carbon, or those secondarily evolved from such organisms."
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Affiliation(s)
- Ferran Garcia‐Pichel
- Center for Fundamental and Applied Microbiomics & School of Life SciencesArizona State UniversityTempeArizona85287USA
| | - Jonathan P. Zehr
- Department of Ocean SciencesUniversity of CaliforniaSanta CruzCalifornia95064USA
| | - Debashish Bhattacharya
- Department of Biochemistry and MicrobiologyRutgers UniversityNew BrunswickNew Jersey08901USA
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23
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Wilson ST, Hawco NJ, Armbrust EV, Barone B, Björkman KM, Boysen AK, Burgos M, Burrell TJ, Casey JR, DeLong EF, Dugenne M, Dutkiewicz S, Dyhrman ST, Ferrón S, Follows MJ, Foreman RK, Funkey CP, Harke MJ, Henke BA, Hill CN, Hynes AM, Ingalls AE, Jahn O, Kelly RL, Knapp AN, Letelier RM, Ribalet F, Shimabukuro EM, Tabata RKS, Turk-Kubo KA, White AE, Zehr JP, John S, Karl DM. Kīlauea lava fuels phytoplankton bloom in the North Pacific Ocean. Science 2019; 365:1040-1044. [DOI: 10.1126/science.aax4767] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 07/17/2019] [Indexed: 11/02/2022]
Affiliation(s)
- Samuel T. Wilson
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Nicholas J. Hawco
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Benedetto Barone
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Karin M. Björkman
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Angela K. Boysen
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Macarena Burgos
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Timothy J. Burrell
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - John R. Casey
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Edward F. DeLong
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Mathilde Dugenne
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Stephanie Dutkiewicz
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sonya T. Dyhrman
- Department of Earth and Environmental Sciences, Columbia University, Palisades, NY 10964, USA
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
| | - Sara Ferrón
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Michael J. Follows
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Rhea K. Foreman
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Carolina P. Funkey
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Matthew J. Harke
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA
| | - Britt A. Henke
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Christopher N. Hill
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Annette M. Hynes
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Anitra E. Ingalls
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Oliver Jahn
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Rachel L. Kelly
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Angela N. Knapp
- Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
| | - Ricardo M. Letelier
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Francois Ribalet
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Eric M. Shimabukuro
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Ryan K. S. Tabata
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Kendra A. Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Angelicque E. White
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Seth John
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - David M. Karl
- Department of Oceanography, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai‘i at Manoa, Honolulu, HI 96822, USA
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24
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Pereira N, Shilova IN, Zehr JP. Use of the high-affinity phosphate transporter gene, pstS, as an indicator for phosphorus stress in the marine diazotroph Crocosphaera watsonii (Chroococcales, Cyanobacteria). J Phycol 2019; 55:752-761. [PMID: 30929262 DOI: 10.1111/jpy.12863] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 03/18/2019] [Indexed: 06/09/2023]
Abstract
The marine diazotroph Crocosphaera watsonii provides fixed carbon (C) and nitrogen (N) to open-ocean regimes, where nutrient deficiency controls productivity. The growth of Crocosphaera can be limited by low phosphorus (P) concentrations in these oligotrophic environments. Biomarkers such as the high-affinity ABC transporter phosphate-binding gene, pstS, are commonly used to monitor when such organisms are under P stress; however, transcriptional regulation of these markers is often complex and not well-understood. In this study, we interrogated changes in pstS transcript levels in C. watsonii cells under P starvation, and in response to added dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), and changing light levels. We observed elevated relative pstS transcript levels in C. watsonii WH8501 at DIP concentrations below 60 and above 20 nmol · L-1 . Transcript levels were suppressed by both inorganic and bioavailable organic phosphorus; however, the P stress response was more sensitive to DIP than DOP sources. Increasing light intensity resulted in increased relative pstS transcript abundances independently of low external P, and seemed to exacerbate the physiological effects of P stress. The variable response to different P compounds and rapid and transient influence of high light on pstS transcript abundances suggests that pstS is an indicator of internal P status in Crocosphaera.
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Affiliation(s)
- Nicole Pereira
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
- Second Genome, 341 Allerton Avenue, South San Francisco, California, 94080, USA
| | - Irina N Shilova
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
- Second Genome, 341 Allerton Avenue, South San Francisco, California, 94080, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, 1156 High Street, Santa Cruz, California, 95064, USA
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25
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Moreira-Coello V, Mouriño-Carballido B, Marañón E, Fernández-Carrera A, Bode A, Sintes E, Zehr JP, Turk-Kubo K, Varela MM. Temporal variability of diazotroph community composition in the upwelling region off NW Iberia. Sci Rep 2019; 9:3737. [PMID: 30842510 PMCID: PMC6403370 DOI: 10.1038/s41598-019-39586-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 01/22/2019] [Indexed: 11/24/2022] Open
Abstract
Knowledge of the ecology of N2-fixing (diazotrophic) plankton is mainly limited to oligotrophic (sub)tropical oceans. However, diazotrophs are widely distributed and active throughout the global ocean. Likewise, relatively little is known about the temporal dynamics of diazotrophs in productive areas. Between February 2014 and December 2015, we carried out 9 one-day samplings in the temperate northwestern Iberian upwelling system to investigate the temporal and vertical variability of the diazotrophic community and its relationship with hydrodynamic forcing. In downwelling conditions, characterized by deeper mixed layers and a homogeneous water column, non-cyanobacterial diazotrophs belonging mainly to nifH clusters 1G (Gammaproteobacteria) and 3 (putative anaerobes) dominated the diazotrophic community. In upwelling and relaxation conditions, affected by enhanced vertical stratification and hydrographic variability, the community was more heterogeneous vertically but less diverse, with prevalence of UCYN-A (unicellular cyanobacteria, subcluster 1B) and non-cyanobacterial diazotrophs from clusters 1G and 3. Oligotyping analysis of UCYN-A phylotype showed that UCYN-A2 sublineage was the most abundant (74%), followed by UCYN-A1 (23%) and UCYN-A4 (2%). UCYN-A1 oligotypes exhibited relatively low frequencies during the three hydrographic conditions, whereas UCYN-A2 showed higher abundances during upwelling and relaxation. Our findings show the presence of a diverse and temporally variable diazotrophic community driven by hydrodynamic forcing in an upwelling system.
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Affiliation(s)
| | | | - Emilio Marañón
- Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Vigo, Spain
| | | | - Antonio Bode
- Instituto Español de Oceanografía, A Coruña, Spain
| | - Eva Sintes
- Instituto Español de Oceanografía, Baleares, Spain
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, California, USA
| | - Kendra Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, California, USA
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26
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Cornejo-Castillo FM, Muñoz-Marín MDC, Turk-Kubo KA, Royo-Llonch M, Farnelid H, Acinas SG, Zehr JP. UCYN-A3, a newly characterized open ocean sublineage of the symbiotic N 2 -fixing cyanobacterium Candidatus Atelocyanobacterium thalassa. Environ Microbiol 2018; 21:111-124. [PMID: 30255541 DOI: 10.1111/1462-2920.14429] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 09/06/2018] [Accepted: 09/22/2018] [Indexed: 12/01/2022]
Abstract
The symbiotic unicellular cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) is one of the most abundant and widespread nitrogen (N2 )-fixing cyanobacteria in the ocean. Although it remains uncultivated, multiple sublineages have been detected based on partial nitrogenase (nifH) gene sequences, including the four most commonly detected sublineages UCYN-A1, UCYN-A2, UCYN-A3 and UCYN-A4. However, very little is known about UCYN-A3 beyond the nifH sequences from nifH gene diversity surveys. In this study, single cell sorting, DNA sequencing, qPCR and CARD-FISH assays revealed discrepancies involving the identification of sublineages, which led to new information on the diversity of the UCYN-A symbiosis. 16S rRNA and nifH gene sequencing on single sorted cells allowed us to identify the 16S rRNA gene of the uncharacterized UCYN-A3 sublineage. We designed new CARD-FISH probes that allowed us to distinguish and observe UCYN-A2 in a coastal location (SIO Pier; San Diego) and UCYN-A3 in an open ocean location (Station ALOHA; Hawaii). Moreover, we reconstructed about 13% of the UCYN-A3 genome from Tara Oceans metagenomic data. Finally, our findings unveil the UCYN-A3 symbiosis in open ocean waters suggesting that the different UCYN-A sublineages are distributed along different size fractions of the plankton defined by the cell-size ranges of their prymnesiophyte hosts.
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Affiliation(s)
- Francisco M Cornejo-Castillo
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.,Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Maria Del Carmen Muñoz-Marín
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.,Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario, Universidad de Córdoba, Córdoba, Spain
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Marta Royo-Llonch
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Hanna Farnelid
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.,Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden
| | - Silvia G Acinas
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM), CSIC, Barcelona, Spain
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
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27
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Robidart JC, Magasin JD, Shilova IN, Turk-Kubo KA, Wilson ST, Karl DM, Scholin CA, Zehr JP. Effects of nutrient enrichment on surface microbial community gene expression in the oligotrophic North Pacific Subtropical Gyre. ISME J 2018; 13:374-387. [PMID: 30254320 DOI: 10.1038/s41396-018-0280-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 07/26/2018] [Accepted: 08/26/2018] [Indexed: 11/09/2022]
Abstract
Marine microbial communities are critical for biogeochemical cycles and the productivity of ocean ecosystems. Primary productivity in the surface ocean is constrained by nutrients which are supplied, in part, by mixing with deeper water. Little is known about the time scales, frequency, or impact of mixing on microbial communities. We combined in situ sampling using the Environmental Sample Processor and a small-scale mixing experiment with lower euphotic zone water to determine how individual populations respond to mixing. Transcriptional responses were measured using the MicroTOOLs (Microbiological Targets for Ocean Observing Laboratories) microarray, which targets all three domains of life and viruses. The experiment showed that mixing substantially affects photosynthetic taxa as expected, but surprisingly also showed that populations respond differently to unfiltered deep water which contains particles (organisms and detritus) compared to filtered deep water that only contains nutrients and viruses, pointing to the impact of biological interactions associated with these events. Comparison between experimental and in situ population transcription patterns indicated that manipulated populations can serve as analogs for natural populations, and that natural populations may be frequently or continuously responding to nutrients from deeper waters. Finally, this study also shows that the microarray approach, which is complementary to metatranscriptomic sequencing, is useful for determining the physiological status of in situ microbial communities.
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Affiliation(s)
- J C Robidart
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA.,National Oceanography Centre, Southampton, UK
| | - J D Magasin
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - I N Shilova
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA.,Second Genome, South San Francisco, CA, USA
| | - K A Turk-Kubo
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - S T Wilson
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI, USA.,Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - D M Karl
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI, USA.,Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - C A Scholin
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - J P Zehr
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA.
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28
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Harke MJ, Frischkorn KR, Haley ST, Aylward FO, Zehr JP, Dyhrman ST. Periodic and coordinated gene expression between a diazotroph and its diatom host. ISME J 2018; 13:118-131. [PMID: 30116042 DOI: 10.1038/s41396-018-0262-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/28/2018] [Accepted: 07/28/2018] [Indexed: 01/30/2023]
Abstract
In the surface ocean, light fuels photosynthetic carbon fixation of phytoplankton, playing a critical role in ecosystem processes including carbon export to the deep sea. In oligotrophic oceans, diatom-diazotroph associations (DDAs) play a keystone role in ecosystem function because diazotrophs can provide otherwise scarce biologically available nitrogen to the diatom host, fueling growth and subsequent carbon sequestration. Despite their importance, relatively little is known about the nature of these associations in situ. Here we used metatranscriptomic sequencing of surface samples from the North Pacific Subtropical Gyre (NPSG) to reconstruct patterns of gene expression for the diazotrophic symbiont Richelia and we examined how these patterns were integrated with those of the diatom host over day-night transitions. Richelia exhibited significant diel signals for genes related to photosynthesis, N2 fixation, and resource acquisition, among other processes. N2 fixation genes were significantly co-expressed with host nitrogen uptake and metabolism, as well as potential genes involved in carbon transport, which may underpin the exchange of nitrogen and carbon within this association. Patterns of expression suggested cell division was integrated between the host and symbiont across the diel cycle. Collectively these data suggest that symbiont-host physiological ecology is strongly interconnected in the NPSG.
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Affiliation(s)
- Matthew J Harke
- Lamont-Doherty Earth Observatory, Biology and Paleo Environment, Columbia University, Palisades, NY, USA
| | - Kyle R Frischkorn
- Lamont-Doherty Earth Observatory, Biology and Paleo Environment, Columbia University, Palisades, NY, USA.,Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
| | - Sheean T Haley
- Lamont-Doherty Earth Observatory, Biology and Paleo Environment, Columbia University, Palisades, NY, USA
| | - Frank O Aylward
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | | | - Sonya T Dyhrman
- Lamont-Doherty Earth Observatory, Biology and Paleo Environment, Columbia University, Palisades, NY, USA. .,Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA.
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29
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Farnelid H, Turk-Kubo K, Ploug H, Ossolinski JE, Collins JR, Van Mooy BAS, Zehr JP. Diverse diazotrophs are present on sinking particles in the North Pacific Subtropical Gyre. ISME J 2018; 13:170-182. [PMID: 30116043 PMCID: PMC6299005 DOI: 10.1038/s41396-018-0259-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/03/2018] [Accepted: 07/26/2018] [Indexed: 11/09/2022]
Abstract
Sinking particles transport carbon and nutrients from the surface ocean into the deep sea and are considered hot spots for bacterial diversity and activity. In the oligotrophic oceans, nitrogen (N2)-fixing organisms (diazotrophs) are an important source of new N but the extent to which these organisms are present and exported on sinking particles is not well known. Sinking particles were collected every 6 h over a 2-day period using net traps deployed at 150 m in the North Pacific Subtropical Gyre. The bacterial community and composition of diazotrophs associated with individual and bulk sinking particles was assessed using 16S rRNA and nifH gene amplicon sequencing. The bacterial community composition in bulk particles remained remarkably consistent throughout time and space while large variations of individually picked particles were observed. This difference suggests that unique biogeochemical conditions within individual particles may offer distinct ecological niches for specialized bacterial taxa. Compared to surrounding seawater, particle samples were enriched in different size classes of globally significant N2-fixing cyanobacteria including Trichodesmium, symbionts of diatoms, and the unicellular cyanobacteria Crocosphaera and UCYN-A. The particles also contained nifH gene sequences of diverse non-cyanobacterial diazotrophs suggesting that particles could be loci for N2 fixation by heterotrophic bacteria. The results demonstrate that diverse diazotrophs were present on particles and that new N may thereby be directly exported from surface waters on sinking particles.
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Affiliation(s)
- Hanna Farnelid
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA. .,Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
| | - Kendra Turk-Kubo
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA
| | - Helle Ploug
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Justin E Ossolinski
- Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - James R Collins
- Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.,MIT/WHOI Joint Program in Oceanography, University of Washington, Seattle, WA, USA.,School of Oceanography and eScience Institute, University of Washington, Seattle, WA, USA
| | - Benjamin A S Van Mooy
- Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California at Santa Cruz, Santa Cruz, CA, USA
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30
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Turk-Kubo KA, Connell P, Caron D, Hogan ME, Farnelid HM, Zehr JP. In Situ Diazotroph Population Dynamics Under Different Resource Ratios in the North Pacific Subtropical Gyre. Front Microbiol 2018; 9:1616. [PMID: 30090092 PMCID: PMC6068237 DOI: 10.3389/fmicb.2018.01616] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 06/28/2018] [Indexed: 11/13/2022] Open
Abstract
Major advances in understanding the diversity, distribution, and activity of marine N2-fixing microorganisms (diazotrophs) have been made in the past decades, however, large gaps in knowledge remain about the environmental controls on growth and mortality rates. In order to measure diazotroph net growth rates and microzooplankton grazing rates on diazotrophs, nutrient perturbation experiments and dilution grazing experiments were conducted using free-floating in situ incubation arrays in the vicinity of Station ALOHA in March 2016. Net growth rates for targeted diazotroph taxa as well as Prochlorococcus, Synechococcus and photosynthetic picoeukaryotes were determined under high (H) and low (L) nitrate:phosphate (NP) ratio conditions at four depths in the photic zone (25, 45, 75, and 100 m) using quantitative PCR and flow cytometry. Changes in the prokaryote community composition in response to HNP and LNP treatments were characterized using 16S rRNA variable region tag sequencing. Microzooplankton grazing rates on diazotrophs were measured using a modified dilution technique at two depths in the photic zone (15 and 125 m). Net growth rates for most of the targeted diazotrophs after 48 h were not stimulated as expected by LNP conditions, rather enhanced growth rates were often measured in HNP treatments. Interestingly, net growth rates of the uncultivated prymnesiophyte symbiont UCYN-A1 were stimulated in HNP treatments at 75 and 100 m, suggesting that N used for growth was acquired through continuing to fix N2 in the presence of nitrate. Net growth rates for UCYN-A1, UCYN-C, Crocosphaera sp. (UCYN-B) and the diatom symbiont Richelia (associated with Rhizosolenia) were uniformly high at 45 m (up to 1.6 ± 0.5 d-1), implying that all were growing optimally at the onset of the experiment at that depth. Differences in microzooplankton grazing rates on UCYN-A1 and UCYN-C in 15 m waters indicate that the grazer assemblage preyed preferentially on UCYN-A1. Deeper in the water column (125 m), both diazotrophs were grazed at substantial rates, suggesting grazing pressure may increase with depth in the photic zone. Constraining in situ diazotroph growth and mortality rates are important steps for improving parameterization for diazotrophs in global ecosystem models.
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Affiliation(s)
- Kendra A. Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Paige Connell
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - David Caron
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Mary E. Hogan
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Hanna M. Farnelid
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
- Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
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31
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Henke BA, Turk-Kubo KA, Bonnet S, Zehr JP. Distributions and Abundances of Sublineages of the N 2-Fixing Cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) in the New Caledonian Coral Lagoon. Front Microbiol 2018; 9:554. [PMID: 29674998 PMCID: PMC5895702 DOI: 10.3389/fmicb.2018.00554] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 03/12/2018] [Indexed: 11/21/2022] Open
Abstract
Nitrogen (N2) fixation is a major source of nitrogen that supports primary production in the vast oligotrophic areas of the world’s oceans. The Western Tropical South Pacific has recently been identified as a hotspot for N2 fixation. In the Noumea lagoon (New Caledonia), high abundances of the unicellular N2-fixing cyanobacteria group A (UCYN-A), coupled with daytime N2 fixation rates associated with the <10 μm size fraction, suggest UCYN-A may be an important diazotroph (N2-fixer) in this region. However, little is known about the seasonal variability and diversity of UCYN-A there. To assess this, surface waters from a 12 km transect from the mouth of the Dumbea River to the Dumbea Pass were sampled monthly between July 2012 and March 2014. UCYN-A abundances for two of the defined sublineages, UCYN-A1 and UCYN-A2, were quantified using qPCR targeting the nifH gene, and the nifH-based diversity of UCYN-A was characterized by identifying oligotypes, alternative taxonomic units defined by nucleotide positions with high variability. UCYN-A abundances were dominated by the UCYN-A1 sublineage, peaked in September and October and could be predicted by a suite of nine environmental parameters. At the sublineage level, UCYN-A1 abundances could be predicted based on lower temperatures (<23°C), nitrate concentrations, precipitation, wind speed, while UCYN-A2 abundances could be predicted based on silica, and chlorophyll a concentrations, wind direction, precipitation, and wind speed. Using UCYN-A nifH oligotyping, similar environmental variables explained the relative abundances of sublineages and their associated oligotypes, with the notable exception of the UCYN-A2 oligotype (oligo43) which had relative abundance patterns distinct from the dominant UCYN-A2 oligotype (oligo3). The results support an emerging pattern that UCYN-A is comprised of a diverse group of strains, with sublineages that may have different ecological niches. By identifying environmental factors that influence the composition and abundance of UCYN-A sublineages, this study helps to explain global UCYN-A abundance patterns, and is important for understanding the significance of N2 fixation at local and global scales.
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Affiliation(s)
- Britt A Henke
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Sophie Bonnet
- IRD, MIO, UM 110 - IRD Centre of Noumea, Aix-Marseille University, University of South Toulon Var, CNRS/INSU, Noumea, France
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United States
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Affiliation(s)
- Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.
| | - Joshua S Weitz
- School of Biological Sciences & School of Physics, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA.
| | - Ian Joint
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, Devon, PL1 2PB, UK.
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Wilson ST, Aylward FO, Ribalet F, Barone B, Casey JR, Connell PE, Eppley JM, Ferrón S, Fitzsimmons JN, Hayes CT, Romano AE, Turk-Kubo KA, Vislova A, Armbrust EV, Caron DA, Church MJ, Zehr JP, Karl DM, DeLong EF. Coordinated regulation of growth, activity and transcription in natural populations of the unicellular nitrogen-fixing cyanobacterium Crocosphaera. Nat Microbiol 2017; 2:17118. [DOI: 10.1038/nmicrobiol.2017.118] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 06/23/2017] [Indexed: 01/01/2023]
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Turk-Kubo KA, Farnelid HM, Shilova IN, Henke B, Zehr JP. Distinct ecological niches of marine symbiotic N 2 -fixing cyanobacterium Candidatus Atelocyanobacterium thalassa sublineages. J Phycol 2017; 53:451-461. [PMID: 27992651 DOI: 10.1111/jpy.12505] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 11/17/2016] [Indexed: 06/06/2023]
Abstract
A recently described symbiosis between the metabolically streamlined nitrogen-fixing cyanobacterium UCYN-A and a single-celled eukaryote prymnesiophyte alga is widely distributed throughout tropical and subtropical marine waters, and is thought to contribute significantly to nitrogen fixation in these regions. Several UCYN-A sublineages have been defined based on UCYN-A nitrogenase (nifH) sequences. Due to the low abundances of UCYN-A in the global oceans, currently existing molecular techniques are limited for detecting and quantifying these organisms. A targeted approach is needed to adequately characterize the diversity of this important marine cyanobacterium, and to advance understanding of its ecological importance. We present findings on the distribution of UCYN-A sublineages based on high throughput sequencing of UCYN-A nifH PCR amplicons from 78 samples distributed throughout many major oceanic provinces. These UCYN-A nifH fragments were used to define oligotypes, alternative taxonomic units defined by nucleotide positions with high variability. The data set was dominated by a single oligotype associated with the UCYN-A1 sublineage, consistent with previous observations of relatively high abundances in tropical and subtropical regions. However, this analysis also revealed for the first time the widespread distribution of the UCYN-A3 sublineage in oligotrophic waters. Furthermore, distinct assemblages of UCYN-A oligotypes were found in oligotrophic and coastally influenced waters. This unique data set provides a framework for determining the environmental controls on UCYN-A distributions and the ecological importance of the different sublineages.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, California, 95064, USA
| | - Hanna M Farnelid
- Ocean Sciences Department, University of California, Santa Cruz, California, 95064, USA
- Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, 392 34, Kalmar, Sweden
| | - Irina N Shilova
- Ocean Sciences Department, University of California, Santa Cruz, California, 95064, USA
| | - Britt Henke
- Ocean Sciences Department, University of California, Santa Cruz, California, 95064, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, California, 95064, USA
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Zehr JP, Shilova IN, Farnelid HM, Muñoz-Marín MDC, Turk-Kubo KA. Erratum: Unusual marine unicellular symbiosis with the nitrogen-fixing cyanobacterium UCYN-A. Nat Microbiol 2017; 2:17016. [DOI: 10.1038/nmicrobiol.2017.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Fernández-Méndez M, Turk-Kubo KA, Buttigieg PL, Rapp JZ, Krumpen T, Zehr JP, Boetius A. Diazotroph Diversity in the Sea Ice, Melt Ponds, and Surface Waters of the Eurasian Basin of the Central Arctic Ocean. Front Microbiol 2016; 7:1884. [PMID: 27933047 PMCID: PMC5120112 DOI: 10.3389/fmicb.2016.01884] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/09/2016] [Indexed: 11/13/2022] Open
Abstract
The Eurasian basin of the Central Arctic Ocean is nitrogen limited, but little is known about the presence and role of nitrogen-fixing bacteria. Recent studies have indicated the occurrence of diazotrophs in Arctic coastal waters potentially of riverine origin. Here, we investigated the presence of diazotrophs in ice and surface waters of the Central Arctic Ocean in the summer of 2012. We identified diverse communities of putative diazotrophs through targeted analysis of the nifH gene, which encodes the iron protein of the nitrogenase enzyme. We amplified 529 nifH sequences from 26 samples of Arctic melt ponds, sea ice and surface waters. These sequences resolved into 43 clusters at 92% amino acid sequence identity, most of which were non-cyanobacterial phylotypes from sea ice and water samples. One cyanobacterial phylotype related to Nodularia sp. was retrieved from sea ice, suggesting that this important functional group is rare in the Central Arctic Ocean. The diazotrophic community in sea-ice environments appear distinct from other cold-adapted diazotrophic communities, such as those present in the coastal Canadian Arctic, the Arctic tundra and glacial Antarctic lakes. Molecular fingerprinting of nifH and the intergenic spacer region of the rRNA operon revealed differences between the communities from river-influenced Laptev Sea waters and those from ice-related environments pointing toward a marine origin for sea-ice diazotrophs. Our results provide the first record of diazotrophs in the Central Arctic and suggest that microbial nitrogen fixation may occur north of 77°N. To assess the significance of nitrogen fixation for the nitrogen budget of the Arctic Ocean and to identify the active nitrogen fixers, further biogeochemical and molecular biological studies are needed.
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Affiliation(s)
- Mar Fernández-Méndez
- HGF-MPG Group for Deep Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine ResearchBremerhaven, Germany; HGF-MPG Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine MicrobiologyBremen, Germany
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California at Santa Cruz, Santa Cruz CA, USA
| | - Pier L Buttigieg
- HGF-MPG Group for Deep Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Bremerhaven, Germany
| | - Josephine Z Rapp
- HGF-MPG Group for Deep Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine ResearchBremerhaven, Germany; HGF-MPG Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine MicrobiologyBremen, Germany
| | - Thomas Krumpen
- Sea Ice Physics Section, Climate Sciences Department, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Bremerhaven, Germany
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California at Santa Cruz, Santa Cruz CA, USA
| | - Antje Boetius
- HGF-MPG Group for Deep Sea Ecology and Technology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine ResearchBremerhaven, Germany; HGF-MPG Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine MicrobiologyBremen, Germany
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Frank IE, Turk-Kubo KA, Zehr JP. Rapid annotation of nifH gene sequences using classification and regression trees facilitates environmental functional gene analysis. Environ Microbiol Rep 2016; 8:905-916. [PMID: 27557869 DOI: 10.1111/1758-2229.12455] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 08/16/2016] [Indexed: 05/22/2023]
Abstract
The nifH gene is a widely used molecular proxy for studying nitrogen fixation. Phylogenetic classification of nifH gene sequences is an essential step in diazotroph community analysis that requires a fast automated solution due to increasing size of environmental sequence libraries and increasing yield of nifH sequences from high-throughput technologies. A novel approach to rapidly classify nifH amino acid sequences into well-defined phylogenetic clusters that provides a common platform for comparative analysis across studies is presented. Phylogenetic group membership can be accurately predicted with decision tree-type statistical models that identify and utilize signature residues in the amino acid sequences. Our classification models were trained and evaluated with a publicly available and manually curated nifH gene database containing cluster annotations. Model-independent sequence sets from diverse ecosystems were used for further assessment of the models' prediction accuracy. The utility of this novel sequence binning approach was demonstrated in a comparative study where joint treatment of diazotroph assemblages from a wide range of habitats identified habitat-specific and widely-distributed diazotrophs and revealed a marine - terrestrial distinction in community composition. Our rapid and automated phylogenetic cluster assignment circumvents extensive phylogenetic analysis of nifH sequences; hence, it saves substantial time and resources in nitrogen fixation studies.
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Affiliation(s)
- Ildiko E Frank
- Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Kendra A Turk-Kubo
- Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
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Abstract
Some cyanobacteria are capable of differentiating a variety of cell types in response to environmental factors. For instance, in low nitrogen conditions, some cyanobacteria form heterocysts, which are specialized for N2 fixation. Many heterocyst-forming cyanobacteria have DNA elements interrupting key N2 fixation genes, elements that are excised during heterocyst differentiation. While the mechanism for the excision of the element has been well-studied, many questions remain regarding the introduction of the elements into the cyanobacterial lineage and whether they have been retained ever since or have been lost and reintroduced. To examine the evolutionary relationships and possible function of DNA sequences that interrupt genes of heterocyst-forming cyanobacteria, we identified and compared 101 interruption element sequences within genes from 38 heterocyst-forming cyanobacterial genomes. The interruption element lengths ranged from about 1 kb (the minimum able to encode the recombinase responsible for element excision), up to nearly 1 Mb. The recombinase gene sequences served as genetic markers that were common across the interruption elements and were used to track element evolution. Elements were found that interrupted 22 different orthologs, only five of which had been previously observed to be interrupted by an element. Most of the newly identified interrupted orthologs encode proteins that have been shown to have heterocyst-specific activity. However, the presence of interruption elements within genes with no known role in N2 fixation, as well as in three non-heterocyst-forming cyanobacteria, indicates that the processes that trigger the excision of elements may not be limited to heterocyst development or that the elements move randomly within genomes. This comprehensive analysis provides the framework to study the history and behavior of these unique sequences, and offers new insight regarding the frequency and persistence of interruption elements in heterocyst-forming cyanobacteria.
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Affiliation(s)
- Jason A. Hilton
- University of California Department of Ocean Sciences, Santa Cruz, California, United States of America
- * E-mail:
| | - John C. Meeks
- University of California Department of Microbiology and Molecular Genetics, Davis, California, United States of America
| | - Jonathan P. Zehr
- University of California Department of Ocean Sciences, Santa Cruz, California, United States of America
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Pereira N, Shilova IN, Zehr JP. Molecular markers define progressing stages of phosphorus limitation in the nitrogen-fixing cyanobacterium, Crocosphaera. J Phycol 2016; 52:274-282. [PMID: 27037592 DOI: 10.1111/jpy.12396] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 01/19/2016] [Indexed: 06/05/2023]
Abstract
Crocosphaera watsonii is a marine cyanobacterium that frequently inhabits low phosphate environments in oligotrophic oceans. While C. watsonii has the ability to fix atmospheric nitrogen, its growth may be limited by availability of phosphorus. Biomarkers that indicate cellular phosphorus status give insight into how P-limitation can affect the distribution of nitrogen-fixing cyanobacterial populations. However, adaptation to phosphorus stress is complex and one marker may not be sufficient to determine when an organism is P-limited. In this study, we characterized the transcription of key genes, activated during phosphorus stress in C. watsonii WH8501, to determine how transcription changed during the phosphorus stress response. Transcription of pstS, which encodes a high-affinity phosphate binding protein, was discovered to be quickly up-regulated in phosphorus-depleted cells as an immediate stress response; however, its transcription declined after a period of phosphorus starvation. In addition, diel regulation of pstS in C. watsonii WH8501 complicates the interpretation of this marker in field applications. Transcription of the gene coding for the arsenite efflux protein, arsB, was upregulated after pstS in phosphorus limited cells, but it remained upregulated at later stages of phosphorus limitation. These results demonstrate that a single molecular marker does not adequately represent the entire phosphorus stress response in C. watsonii WH8501. Using both markers, the variations in transcriptional response over a range of degrees of phosphorus limitation may be a better approach for defining cellular phosphorus status.
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Affiliation(s)
- Nicole Pereira
- Ocean Science Department, University of California, Santa Cruz, California, 95064, USA
| | - Irina N Shilova
- Ocean Science Department, University of California, Santa Cruz, California, 95064, USA
| | - Jonathan P Zehr
- Ocean Science Department, University of California, Santa Cruz, California, 95064, USA
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Farnelid HM, Turk-Kubo KA, Zehr JP. Identification of Associations between Bacterioplankton and Photosynthetic Picoeukaryotes in Coastal Waters. Front Microbiol 2016; 7:339. [PMID: 27148165 PMCID: PMC4834442 DOI: 10.3389/fmicb.2016.00339] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/03/2016] [Indexed: 01/10/2023] Open
Abstract
Photosynthetic picoeukaryotes are significant contributors to marine primary productivity. Associations between marine bacterioplankton and picoeukaryotes frequently occur and can have large biogeochemical impacts. We used flow cytometry to sort cells from seawater to identify non-eukaryotic phylotypes that are associated with photosynthetic picoeukaryotes. Samples were collected at the Santa Cruz wharf on Monterey Bay, CA, USA during summer and fall, 2014. The phylogeny of associated microbes was assessed through 16S rRNA gene amplicon clone and Illumina MiSeq libraries. The most frequently detected bacterioplankton phyla within the photosynthetic picoeukaryote sorts were Proteobacteria (Alphaproteobacteria and Gammaproteobacteria) and Bacteroidetes. Intriguingly, the presence of free-living bacterial genera in the photosynthetic picoeukaryote sorts could suggest that some of the photosynthetic picoeukaryotes were mixotrophs. However, the occurrence of bacterial sequences, which were not prevalent in the corresponding bulk seawater samples, indicates that there was also a selection for specific OTUs in association with photosynthetic picoeukaryotes suggesting specific functional associations. The results show that diverse bacterial phylotypes are found in association with photosynthetic picoeukaryotes. Taxonomic identification of these associations is a prerequisite for further characterizing and to elucidate their metabolic pathways and ecological functions.
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Affiliation(s)
- Hanna M Farnelid
- Ocean Sciences Department, University of California at Santa CruzSanta Cruz, CA, USA; Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus UniversityKalmar, Sweden
| | - Kendra A Turk-Kubo
- Ocean Sciences Department, University of California at Santa Cruz Santa Cruz, CA, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California at Santa Cruz Santa Cruz, CA, USA
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Bench SR, Frank I, Robidart J, Zehr JP. Two subpopulations of C
rocosphaera watsonii
have distinct distributions in the North and South Pacific. Environ Microbiol 2016; 18:514-24. [DOI: 10.1111/1462-2920.13180] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Revised: 11/25/2015] [Accepted: 12/04/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Shellie R. Bench
- Department of Ocean Sciences; University of California Santa Cruz; 1156 High Street Santa Cruz CA 95064 USA
| | - Ildiko Frank
- Department of Ocean Sciences; University of California Santa Cruz; 1156 High Street Santa Cruz CA 95064 USA
| | - Julie Robidart
- Department of Ocean Sciences; University of California Santa Cruz; 1156 High Street Santa Cruz CA 95064 USA
- Monterey Bay Aquarium Research Institute; 7700 Sandholdt Road Moss Landing CA 95039 USA
- Center for Microbial Oceanography: Research and Education; University of Hawaii; 1950 East-West Road Honolulu HI 96822 USA
| | - Jonathan P. Zehr
- Department of Ocean Sciences; University of California Santa Cruz; 1156 High Street Santa Cruz CA 95064 USA
- Monterey Bay Aquarium Research Institute; 7700 Sandholdt Road Moss Landing CA 95039 USA
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Shilova IN, Robidart JC, DeLong EF, Zehr JP. Genetic Diversity Affects the Daily Transcriptional Oscillations of Marine Microbial Populations. PLoS One 2016; 11:e0146706. [PMID: 26751368 PMCID: PMC4709009 DOI: 10.1371/journal.pone.0146706] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 12/21/2015] [Indexed: 11/18/2022] Open
Abstract
Marine microbial communities are genetically diverse but have robust synchronized daily transcriptional patterns at the genus level that are similar across a wide variety of oceanic regions. We developed a microarray-inspired gene-centric approach to resolve transcription of closely-related but distinct strains/ecotypes in high-throughput sequence data. Applying this approach to the existing metatranscriptomics datasets collected from two different oceanic regions, we found unique and variable patterns of transcription by individual taxa within the abundant picocyanobacteria Prochlorococcus and Synechococcus, the alpha Proteobacterium Pelagibacter and the eukaryotic picophytoplankton Ostreococcus. The results demonstrate that marine microbial taxa respond differentially to variability in space and time in the ocean. These intra-genus individual transcriptional patterns underlie whole microbial community responses, and the approach developed here facilitates deeper insights into microbial population dynamics.
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Affiliation(s)
- Irina N. Shilova
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Julie C. Robidart
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Edward F. DeLong
- School of Ocean and Earth Science and Technology, University of Hawai’i at Manoa, Honolulu, Hawaii, United States of America
| | - Jonathan P. Zehr
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- * E-mail:
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43
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Affiliation(s)
- Jonathan P. Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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Hilton JA, Satinsky BM, Doherty M, Zielinski B, Zehr JP. Metatranscriptomics of N2-fixing cyanobacteria in the Amazon River plume. ISME J 2014; 9:1557-69. [PMID: 25514535 DOI: 10.1038/ismej.2014.240] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 11/04/2014] [Accepted: 11/10/2014] [Indexed: 11/09/2022]
Abstract
Biological N2 fixation is an important nitrogen source for surface ocean microbial communities. However, nearly all information on the diversity and gene expression of organisms responsible for oceanic N2 fixation in the environment has come from targeted approaches that assay only a small number of genes and organisms. Using genomes of diazotrophic cyanobacteria to extract reads from extensive meta-genomic and -transcriptomic libraries, we examined diazotroph diversity and gene expression from the Amazon River plume, an area characterized by salinity and nutrient gradients. Diazotroph genome and transcript sequences were most abundant in the transitional waters compared with lower salinity or oceanic water masses. We were able to distinguish two genetically divergent phylotypes within the Hemiaulus-associated Richelia sequences, which were the most abundant diazotroph sequences in the data set. Photosystem (PS)-II transcripts in Richelia populations were much less abundant than those in Trichodesmium, and transcripts from several Richelia PS-II genes were absent, indicating a prominent role for cyclic electron transport in Richelia. In addition, there were several abundant regulatory transcripts, including one that targets a gene involved in PS-I cyclic electron transport in Richelia. High sequence coverage of the Richelia transcripts, as well as those from Trichodesmium populations, allowed us to identify expressed regions of the genomes that had been overlooked by genome annotations. High-coverage genomic and transcription analysis enabled the characterization of distinct phylotypes within diazotrophic populations, revealed a distinction in a core process between dominant populations and provided evidence for a prominent role for noncoding RNAs in microbial communities.
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Affiliation(s)
- Jason A Hilton
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
| | | | - Mary Doherty
- Department of Biology, Rhodes College, Memphis, TN, USA
| | - Brian Zielinski
- College of Marine Science, University of South Florida, St Petersburg, FL, USA
| | - Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
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Heller P, Tripp HJ, Turk-Kubo K, Zehr JP. ARBitrator: a software pipeline for on-demand retrieval of auto-curated nifH sequences from GenBank. ACTA ACUST UNITED AC 2014; 30:2883-90. [PMID: 24990605 DOI: 10.1093/bioinformatics/btu417] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
MOTIVATION Studies of the biochemical functions and activities of uncultivated microorganisms in the environment require analysis of DNA sequences for phylogenetic characterization and for the development of sequence-based assays for the detection of microorganisms. The numbers of sequences for genes that are indicators of environmentally important functions such as nitrogen (N2) fixation have been rapidly growing over the past few decades. Obtaining these sequences from the National Center for Biotechnology Information's GenBank database is problematic because of annotation errors, nomenclature variation and paralogues; moreover, GenBank's structure and tools are not conducive to searching solely by function. For some genes, such as the nifH gene commonly used to assess community potential for N2 fixation, manual collection and curation are becoming intractable because of the large number of sequences in GenBank and the large number of highly similar paralogues. If analysis is to keep pace with sequence discovery, an automated retrieval and curation system is necessary. RESULTS ARBitrator uses a two-step process composed of a broad collection of potential homologues followed by screening with a best hit strategy to conserved domains. 34 420 nifH sequences were identified in GenBank as of November 20, 2012. The false-positive rate is ∼0.033%. ARBitrator rapidly updates a public nifH sequence database, and we show that it can be adapted for other genes. AVAILABILITY AND IMPLEMENTATION Java source and executable code are freely available to non-commercial users at http://pmc.ucsc.edu/∼wwwzehr/research/database/. CONTACT zehrj@ucsc.edu SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION is available at Bioinformatics online.
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Affiliation(s)
- Philip Heller
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA, Department of Energy (DOE) Joint Genome Institute, Walnut Creek, CA 94598, USA and Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - H James Tripp
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA, Department of Energy (DOE) Joint Genome Institute, Walnut Creek, CA 94598, USA and Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Kendra Turk-Kubo
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA, Department of Energy (DOE) Joint Genome Institute, Walnut Creek, CA 94598, USA and Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
| | - Jonathan P Zehr
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA, Department of Energy (DOE) Joint Genome Institute, Walnut Creek, CA 94598, USA and Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA
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Thompson A, Carter BJ, Turk-Kubo K, Malfatti F, Azam F, Zehr JP. Genetic diversity of the unicellular nitrogen-fixing cyanobacteria UCYN-A and its prymnesiophyte host. Environ Microbiol 2014; 16:3238-49. [PMID: 24761991 DOI: 10.1111/1462-2920.12490] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 04/16/2014] [Indexed: 11/30/2022]
Abstract
Symbiotic interactions between nitrogen-fixing prokaryotes and photosynthetic eukaryotes are an integral part of biological nitrogen fixation at a global scale. One of these partnerships involves the cyanobacterium UCYN-A, which has been found in partnership with an uncultivated unicellular prymnesiophyte alga in open-ocean and coastal environments. Phylogenetic analysis of the UCYN-A nitrogenase gene (nifH) showed that the UCYN-A lineage is represented by three distinct clades, referred to herein as UCYN-A1, UCYN-A2 and UCYN-A3, which appear to have overlapping and distinct geographic distributions. The relevance of UCYN-A's genetic diversity to its symbiosis and ecology was explored through combining flow cytometric cell sorting and molecular techniques to determine the host identity, nifH expression patterns and host cell size of one newly discovered clade, UCYN-A2, at a coastal site. UCYN-A2 nifH expression peaked during daylight hours, which is consistent with expression patterns of the UCYN-A1 clade in the open ocean. However, the cell size of the UCYN-A2 host was significantly larger than UCYN-A1 and host, suggesting adaptation to different environmental conditions. Like the UCYN-A1 host, the UCYN-A2 host was closely related to the genus Braarudosphaera; however, the UCYN-A1 and UCYN-A2 host rRNA sequences clustered into two distinct clades suggesting co-evolution of symbiont and host.
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Affiliation(s)
- Anne Thompson
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, CA, 95064, USA
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Collavino MM, Tripp HJ, Frank IE, Vidoz ML, Calderoli PA, Donato M, Zehr JP, Aguilar OM. nifH pyrosequencing reveals the potential for location-specific soil chemistry to influence N2 -fixing community dynamics. Environ Microbiol 2014; 16:3211-23. [PMID: 25314671 DOI: 10.1111/1462-2920.12423] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 12/19/2013] [Accepted: 01/30/2014] [Indexed: 10/25/2022]
Abstract
A dataset of 87 020 nifH reads and 16 782 unique nifH protein sequences obtained over 2 years from four locations across a gradient of agricultural soil types in Argentina were analysed to provide a detailed and comprehensive picture of the diversity, abundance and responses of the N2 -fixing community in relation to differences in soil chemistry and agricultural practices. Phylogenetic analysis revealed an expected high proportion of Alphaproteobacteria, Betaproteobacteria and Deltaproteobacteria, mainly relatives to Bradyrhizobium and Methylosinus/Methylocystis, but a surprising paucity of Gammaproteobacteria. Analysis of variance and stepwise regression modelling suggested location and treatment-specific influences of soil type on diazotrophic community composition and organic carbon concentrations on nifH diversity. nifH gene abundance, determined by quantitative real-time polymerase chain reaction, was higher in agricultural soils than in non-agricultural soils, and was influenced by soil chemistry under intensive crop rotation but not under monoculture. At some locations, sustainable increased crop yields might be possible through the management of soil chemistry to improve the abundance and diversity of N2 -fixing bacteria.
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Affiliation(s)
- Mónica M Collavino
- Instituto de Botánica del Nordeste (IBONE), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste-CONICET, Corrientes, Argentina; Instituto de Biotecnología y Biología Molecular (IBBM), Universidad Nacional de La Plata-CONICET, La Plata, Argentina
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Abstract
The Vibrionaceae (Vibrio) are a ubiquitous group of metabolically flexible marine bacteria that play important roles in biogeochemical cycling in the ocean. Despite this versatility, little is known about Vibrio diversity and abundances in upwelling regions. The seasonal dynamics of Vibrio populations was examined by analysis of 16S rRNA genes in Monterey Bay (MB), California from April 2006-April 2008 at two long term monitoring stations, C1 and M2. Vibrio phylotypes within MB were diverse, with subpopulations clustering with several different cultured representatives including Allivibrio spp., Vibrio penaecida, and Vibrio splendidus as well as with many unidentified marine environmental bacterial 16S rRNA gene sequences. Total Vibrio population abundances, as well as abundances of a Vibrio sp. subpopulation (MBAY Vib7) and an Allivibrio sp. subpopulation (MBAY Vib4) were examined in the context of environmental parameters from mooring station and CTD cast data. Total Vibrio populations showed some seasonal variability but greater variability was observed within the two subpopulations. MBAY Vib4 was negatively associated with MB upwelling indices and positively correlated with oceanic season conditions, when upwelling winds relax and warmer surface waters are present in MB. MBAY Vib7 was also negatively associated with upwelling indices and represented a deeper Vibrio sp. population. Correlation patterns suggest that larger oceanographic conditions affect the dynamics of the populations in MB, rather than specific environmental factors. This study is the first to target and describe the diversity and dynamics of these natural populations in MB and demonstrates that these populations shift seasonally within the region.
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Affiliation(s)
- Sarah Mansergh
- Ocean Sciences Department, University of California at Santa Cruz Santa Cruz, CA, USA
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California at Santa Cruz Santa Cruz, CA, USA
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Robidart JC, Church MJ, Ryan JP, Ascani F, Wilson ST, Bombar D, Marin R, Richards KJ, Karl DM, Scholin CA, Zehr JP. Ecogenomic sensor reveals controls on N2-fixing microorganisms in the North Pacific Ocean. ISME J 2014; 8:1175-85. [PMID: 24477197 DOI: 10.1038/ismej.2013.244] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/28/2013] [Accepted: 12/02/2013] [Indexed: 11/09/2022]
Abstract
Nitrogen-fixing microorganisms (diazotrophs) are keystone species that reduce atmospheric dinitrogen (N2) gas to fixed nitrogen (N), thereby accounting for much of N-based new production annually in the oligotrophic North Pacific. However, current approaches to study N2 fixation provide relatively limited spatiotemporal sampling resolution; hence, little is known about the ecological controls on these microorganisms or the scales over which they change. In the present study, we used a drifting robotic gene sensor to obtain high-resolution data on the distributions and abundances of N2-fixing populations over small spatiotemporal scales. The resulting measurements demonstrate that concentrations of N2 fixers can be highly variable, changing in abundance by nearly three orders of magnitude in less than 2 days and 30 km. Concurrent shipboard measurements and long-term time-series sampling uncovered a striking and previously unrecognized correlation between phosphate, which is undergoing long-term change in the region, and N2-fixing cyanobacterial abundances. These results underscore the value of high-resolution sampling and its applications for modeling the effects of global change.
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Affiliation(s)
- Julie C Robidart
- 1] Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA [2] Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA [3] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Matthew J Church
- 1] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA [2] Department of Oceanography, University of Hawaii, Honolulu, HI, USA
| | - John P Ryan
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - François Ascani
- 1] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA [2] Department of Oceanography, University of Hawaii, Honolulu, HI, USA
| | - Samuel T Wilson
- 1] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA [2] Department of Oceanography, University of Hawaii, Honolulu, HI, USA
| | - Deniz Bombar
- 1] Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA [2] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Roman Marin
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA
| | - Kelvin J Richards
- 1] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA [2] Department of Oceanography, University of Hawaii, Honolulu, HI, USA
| | - David M Karl
- 1] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA [2] Department of Oceanography, University of Hawaii, Honolulu, HI, USA
| | - Christopher A Scholin
- 1] Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA [2] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
| | - Jonathan P Zehr
- 1] Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA [2] Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
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Turk-Kubo KA, Karamchandani M, Capone DG, Zehr JP. The paradox of marine heterotrophic nitrogen fixation: abundances of heterotrophic diazotrophs do not account for nitrogen fixation rates in the Eastern Tropical South Pacific. Environ Microbiol 2014; 16:3095-114. [PMID: 24286454 DOI: 10.1111/1462-2920.12346] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Accepted: 11/23/2013] [Indexed: 11/28/2022]
Abstract
Results of recent modelling efforts imply denitrification-influenced waters, such as those in the Eastern Tropical South Pacific (ETSP), may support high rates of biological nitrogen fixation (BNF), yet little is known about the N2 -fixing microbial community in this region. Our characterization of the ETSP diazotrophic community along a gradient from upwelling-influenced to oligotrophic waters did not detect cyanobacterial diazotrophs commonly found in other open ocean regions. Most of the nifH genes amplified by polymerase chain reaction (PCR) from DNA and RNA samples clustered with γ-proteobacterial nifH sequences, although a novel Trichodesmium phylotype was also recovered. Three quantitative PCR assays were developed to target γ-proteobacterial phylotypes, but all were found to be present at low abundances. An analysis of the expected BNF rates based on abundances and plausible cell-specific N2 fixation rates indicates that these γ-proteobacteria are unlikely to be responsible for previously reported BNF rates from corresponding samples. Therefore, the organisms responsible for the measured BNF rates remain poorly understood. Furthermore, there is little direct evidence, at this time, to support the hypothesis that heterotrophic N2 fixation contributes significantly to oceanic BNF rates based on our analysis of heterotrophic cell-specific N2 fixation rates required to explain BNF rates reported in previously published studies.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, CA, USA
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