1
|
Coale TH, Loconte V, Turk-Kubo KA, Vanslembrouck B, Mak WKE, Cheung S, Ekman A, Chen JH, Hagino K, Takano Y, Nishimura T, Adachi M, Le Gros M, Larabell C, Zehr JP. Nitrogen-fixing organelle in a marine alga. Science 2024; 384:217-222. [PMID: 38603509 DOI: 10.1126/science.adk1075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 02/22/2024] [Indexed: 04/13/2024]
Abstract
Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Biological nitrogen fixation, the reduction of abundant atmospheric nitrogen gas (N2) to biologically available ammonia, is a key metabolic process performed exclusively by prokaryotes. Candidatus Atelocyanobacterium thalassa, or UCYN-A, is a metabolically streamlined N2-fixing cyanobacterium previously reported to be an endosymbiont of a marine unicellular alga. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N2-fixing organelle, or "nitroplast."
Collapse
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
| |
Collapse
|
2
|
Robicheau BM, Tolman J, Desai D, LaRoche J. Microevolutionary patterns in ecotypes of the symbiotic cyanobacterium UCYN-A revealed from a Northwest Atlantic coastal time series. SCIENCE ADVANCES 2023; 9:eadh9768. [PMID: 37774025 PMCID: PMC10541017 DOI: 10.1126/sciadv.adh9768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 08/28/2023] [Indexed: 10/01/2023]
Abstract
UCYN-A is a globally important nitrogen-fixing symbiotic microbe often found in colder regions and coastal areas where nitrogen fixation has been overlooked. We present a 3-year coastal Northwest Atlantic time series of UCYN-A by integrating oceanographic data with weekly nifH and16S rRNA gene sequencing and quantitative PCR assays for UCYN-A ecotypes. High UCYN-A relative abundances dominated by A1 to A4 ecotypes reoccurred annually in the coastal Northwest Atlantic. Although UCYN-A was detected every summer/fall, the ability to observe separate ecotypes may be highly dependent on sampling time given intense interannual and weekly variability of ecotype-specific occurrences. Additionally, much of UCYN-A's rarer diversity was populated by short-lived neutral mutational variants, therefore providing insight into UCYN-A's microevolutionary patterns. For instance, rare ASVs exhibited community composition restructuring annually, while also sharing a common connection to a dominant ASV within each ecotype. Our study provides additional perspectives for interpreting UCYN-A intraspecific diversity and underscores the need for high-resolution datasets when deciphering spatiotemporal ecologies within UCYN-A.
Collapse
Affiliation(s)
- Brent M. Robicheau
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jennifer Tolman
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Dhwani Desai
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- Integrated Microbiome Resource, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Julie LaRoche
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| |
Collapse
|
3
|
von Friesen LW, Paulsen ML, Müller O, Gründger F, Riemann L. Glacial meltwater and seasonality influence community composition of diazotrophs in Arctic coastal and open waters. FEMS Microbiol Ecol 2023; 99:fiad067. [PMID: 37349965 DOI: 10.1093/femsec/fiad067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 04/29/2023] [Accepted: 06/20/2023] [Indexed: 06/24/2023] Open
Abstract
The Arctic Ocean is particularly affected by climate change with unknown consequences for primary productivity. Diazotrophs-prokaryotes capable of converting atmospheric nitrogen to ammonia-have been detected in the often nitrogen-limited Arctic Ocean but distribution and community composition dynamics are largely unknown. We performed amplicon sequencing of the diazotroph marker gene nifH from glacial rivers, coastal, and open ocean regions and identified regionally distinct Arctic communities. Proteobacterial diazotrophs dominated all seasons, epi- to mesopelagic depths and rivers to open waters and, surprisingly, Cyanobacteria were only sporadically identified in coastal and freshwaters. The upstream environment of glacial rivers influenced diazotroph diversity, and in marine samples putative anaerobic sulphate-reducers showed seasonal succession with highest prevalence in summer to polar night. Betaproteobacteria (Burkholderiales, Nitrosomonadales, and Rhodocyclales) were typically found in rivers and freshwater-influenced waters, and Delta- (Desulfuromonadales, Desulfobacterales, and Desulfovibrionales) and Gammaproteobacteria in marine waters. The identified community composition dynamics, likely driven by runoff, inorganic nutrients, particulate organic carbon, and seasonality, imply diazotrophy a phenotype of ecological relevance with expected responsiveness to ongoing climate change. Our study largely expands baseline knowledge of Arctic diazotrophs-a prerequisite to understand underpinning of nitrogen fixation-and supports nitrogen fixation as a contributor of new nitrogen in the rapidly changing Arctic Ocean.
Collapse
Affiliation(s)
- Lisa W von Friesen
- Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark
| | - Maria L Paulsen
- Department of Biology, Aarhus University, Ny Munkegade 114-116, DK-8000 Aarhus, Denmark
| | - Oliver Müller
- Department of Biological Sciences, University of Bergen, Thormøhlens gate 53A, NO-5006 Bergen, Norway
| | - Friederike Gründger
- Department of Biology, Aarhus University, Ny Munkegade 114-116, DK-8000 Aarhus, Denmark
| | - Lasse Riemann
- Department of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark
| |
Collapse
|
4
|
Fletcher-Hoppe C, Yeh YC, Raut Y, Weissman JL, Fuhrman JA. Symbiotic UCYN-A strains co-occurred with El Niño, relaxed upwelling, and varied eukaryotes over 10 years off Southern California. ISME COMMUNICATIONS 2023; 3:63. [PMID: 37355737 PMCID: PMC10290647 DOI: 10.1038/s43705-023-00268-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 05/05/2023] [Accepted: 06/12/2023] [Indexed: 06/26/2023]
Abstract
Biological nitrogen fixation, the conversion of N2 gas into a bioavailable form, is vital to sustaining marine primary production. Studies have shifted beyond traditionally studied tropical diazotrophs. Candidatus Atelocyanobacterium thalassa (or UCYN-A) has emerged as a focal point due to its streamlined metabolism, intimate partnership with a haptophyte host, and broad distribution. Here, we explore the environmental parameters that govern UCYN-A's presence at the San Pedro Ocean Time-series (SPOT), its host specificity, and statistically significant interactions with non-host eukaryotes from 2008-2018. 16S and 18S rRNA gene sequences were amplified by "universal primers" from monthly samples and resolved into Amplicon Sequence Variants, allowing us to observe multiple UCYN-A symbioses. UCYN-A1 relative abundances increased following the 2015-2016 El Niño event. This "open ocean ecotype" was present when coastal upwelling declined, and Ekman transport brought tropical waters into the region. Network analyses reveal all strains of UCYN-A co-occur with dinoflagellates including Lepidodinium, a potential predator, and parasitic Syndiniales. UCYN-A2 appeared to pair with multiple hosts and was not tightly coupled to its predominant host, while UCYN-A1 maintained a strong host-symbiont relationship. These biological relationships are particularly important to study in the context of climate change, which will alter UCYN-A distribution at regional and global scales.
Collapse
Affiliation(s)
- Colette Fletcher-Hoppe
- Marine & Environmental Biology, Department of Biological Sciences, University of Southern California (USC), Los Angeles, CA, USA
| | - Yi-Chun Yeh
- Marine & Environmental Biology, Department of Biological Sciences, University of Southern California (USC), Los Angeles, CA, USA
- Department of Global Ecology, Carnegie Institution for Science, Stanford University, Stanford, CA, USA
| | - Yubin Raut
- Marine & Environmental Biology, Department of Biological Sciences, University of Southern California (USC), Los Angeles, CA, USA
| | - J L Weissman
- Marine & Environmental Biology, Department of Biological Sciences, University of Southern California (USC), Los Angeles, CA, USA
- Schmid College of Science and Technology, Chapman University, Orange, CA, USA
| | - Jed A Fuhrman
- Marine & Environmental Biology, Department of Biological Sciences, University of Southern California (USC), Los Angeles, CA, USA.
| |
Collapse
|
5
|
Takuhei S, Nishimura Y, Yoshizawa S, Takami H, Hamasaki K, Fujiwara A, Nishino S, Harada N. Distribution and survival strategies of endemic and cosmopolitan diazotrophs in the Arctic Ocean. THE ISME JOURNAL 2023:10.1038/s41396-023-01424-x. [PMID: 37217593 DOI: 10.1038/s41396-023-01424-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 04/18/2023] [Accepted: 04/25/2023] [Indexed: 05/24/2023]
Abstract
Dinitrogen (N2) fixation is the major source of reactive nitrogen in the ocean and has been considered to occur specifically in low-latitude oligotrophic oceans. Recent studies have shown that N2 fixation also occurs in the polar regions and thus is a global process, although the physiological and ecological characteristics of polar diazotrophs are not yet known. Here, we successfully reconstructed diazotroph genomes, including that of cyanobacterium UCYN-A (Candidatus 'Atelocyanobacterium thalassa'), from metagenome data corresponding to 111 samples isolated from the Arctic Ocean. These diazotrophs were highly abundant in the Arctic Ocean (max., 1.28% of the total microbial community), suggesting that they have important roles in the Arctic ecosystem and biogeochemical cycles. Further, we show that diazotrophs within genera Arcobacter, Psychromonas, and Oceanobacter are prevalent in the <0.2 µm fraction in the Arctic Ocean, indicating that current methods cannot capture their N2 fixation. Diazotrophs in the Arctic Ocean were either Arctic-endemic or cosmopolitan species from their global distribution patterns. Arctic-endemic diazotrophs, including Arctic UCYN-A, were similar to low-latitude-endemic and cosmopolitan diazotrophs in genome-wide function, however, they had unique gene sets (e.g., diverse aromatics degradation genes), suggesting adaptations to Arctic-specific conditions. Cosmopolitan diazotrophs were generally non-cyanobacteria and commonly had the gene that encodes the cold-inducible RNA chaperone, which presumably makes their survival possible even in deep, cold waters of global ocean and polar surface waters. This study shows global distribution pattern of diazotrophs with their genomes and provides clues to answering the question of how diazotrophs can inhabit polar waters.
Collapse
Affiliation(s)
- Shiozaki Takuhei
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan.
| | - Yosuke Nishimura
- Research Centre for Bioscience and Nanoscience, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, 237-0061, Japan
| | - Susumu Yoshizawa
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
| | - Hideto Takami
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
- Center for Mathematical Science and Advanced Technology, JAMSTEC, Yokohama, 236-0001, Japan
| | - Koji Hamasaki
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 277-8564, Kashiwa, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 113-8657, Bunkyo-ku, Japan
| | - Amane Fujiwara
- Research Institute for Global Change, JAMSTEC, Yokosuka, 237-0061, Japan
| | - Shigeto Nishino
- Research Institute for Global Change, JAMSTEC, Yokosuka, 237-0061, Japan
| | - Naomi Harada
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
- Research Institute for Global Change, JAMSTEC, Yokosuka, 237-0061, Japan
| |
Collapse
|
6
|
Cao M, Wang F, Zhou B, Chen H, Yuan R, Ma S, Geng H, Li J, Lv W, Wang Y, Xing B. Nanoparticles and antibiotics stress proliferated antibiotic resistance genes in microalgae-bacteria symbiotic systems. JOURNAL OF HAZARDOUS MATERIALS 2023; 443:130201. [PMID: 36283215 DOI: 10.1016/j.jhazmat.2022.130201] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/05/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
The comprehensive effect of exogenous pollutants on the dispersal and abundance of antibiotic-resistance genes (ARGs) in the phycosphere, bacterial community and algae-bacteria interaction remains poorly understood. We investigated community structure and abundance of ARGs in free-living (FL) and particle-attached (PA) bacteria in the phycosphere under nanoparticles (silver nanoparticles (AgNPs) and hematite nanoparticles (HemNPs)) and antibiotics (tetracycline and sulfadiazine) stress using high-throughput sequencing and real-time quantitative PCR. Meanwhile, the intrinsic connection of algae-bacteria interaction was explored by transcriptome and metabolome. The results showed that the relative abundance of sulfonamide and tetracycline ARGs in PA and FL bacteria increased 103-129 % and 112-134 %, respectively, under combined stress of nanoparticles and antibiotics. Antibiotics have a greater effect on ARGs than nanoparticles at environmentally relevant concentrations. Proteobacteria, Firmicutes, and Bacteroidetes, as the primary potential hosts of ARGs, were the dominant phyla. Lifestyle, i.e., PA and FL, significantly determined the abundance of ARGs and bacterial communities. Moreover, algae can provide bacteria with nutrients (carbohydrates and amino acids), and can also produce antibacterial substances (fatty acids). This algal-bacterial interaction may indirectly affect the distribution and abundance of ARGs. These findings provide new insights into the distribution and dispersal of ARGs in microalgae-bacteria symbiotic systems.
Collapse
Affiliation(s)
- Manman Cao
- School of Environment, Beijing Normal University, 19 Xinjiekouwai Street, 100875 Beijing, China; School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Fei Wang
- School of Environment, Beijing Normal University, 19 Xinjiekouwai Street, 100875 Beijing, China.
| | - Beihai Zhou
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Huilun Chen
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Rongfang Yuan
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Shuai Ma
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Huanhuan Geng
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Junhong Li
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Wenxiao Lv
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Yan Wang
- School of Energy & Environmental Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China
| | - Baoshan Xing
- Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA
| |
Collapse
|
7
|
Salas K, Cabello AM, Turk-Kubo KA, Zehr JP, Cornejo-Castillo FM. Primer design for the amplification of the ammonium transporter genes from the uncultured haptophyte algal species symbiotic with the marine nitrogen-fixing cyanobacterium UCYN-A1. Front Microbiol 2023; 14:1130695. [PMID: 37138636 PMCID: PMC10150950 DOI: 10.3389/fmicb.2023.1130695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 03/21/2023] [Indexed: 05/05/2023] Open
Abstract
The multiple symbiotic partnerships between closely related species of the haptophyte algae Braarudosphaera bigelowii and the nitrogen-fixing cyanobacteria Candidatus Atelocyanobacterium thalassa (UCYN-A) contribute importantly to the nitrogen and carbon cycles in vast areas of the ocean. The diversity of the eukaryotic 18S rDNA phylogenetic gene marker has helped to identify some of these symbiotic haptophyte species, yet we still lack a genetic marker to assess its diversity at a finer scale. One of such genes is the ammonium transporter (amt) gene, which encodes the protein that might be involved in the uptake of ammonium from UCYN-A in these symbiotic haptophytes. Here, we designed three specific PCR primer sets targeting the amt gene of the haptophyte species (A1-Host) symbiotic with the open ocean UCYN-A1 sublineage, and tested them in samples collected from open ocean and near-shore environments. Regardless of the primer pair used at Station ALOHA, which is where UCYN-A1 is the pre-dominant UCYN-A sublineage, the most abundant amt amplicon sequence variant (ASV) was taxonomically classified as A1-Host. In addition, two out of the three PCR primer sets revealed the existence of closely-related divergent haptophyte amt ASVs (>95% nucleotide identity). These divergent amt ASVs had higher relative abundances than the haptophyte typically associated with UCYN-A1 in the Bering Sea, or co-occurred with the previously identified A1-Host in the Coral Sea, suggesting the presence of new diversity of closely-related A1-Hosts in polar and temperate waters. Therefore, our study reveals an overlooked diversity of haptophytes species with distinct biogeographic distributions partnering with UCYN-A, and provides new primers that will help to gain new knowledge of the UCYN-A/haptophyte symbiosis.
Collapse
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,
| |
Collapse
|
8
|
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] [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.
Collapse
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
| |
Collapse
|
9
|
Wu C, Narale DD, Cui Z, Wang X, Liu H, Xu W, Zhang G, Sun J. Diversity, structure, and distribution of bacterioplankton and diazotroph communities in the Bay of Bengal during the winter monsoon. Front Microbiol 2022; 13:987462. [PMID: 36532434 PMCID: PMC9748438 DOI: 10.3389/fmicb.2022.987462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 11/03/2022] [Indexed: 10/31/2023] Open
Abstract
The Bay of Bengal (BoB) is conventionally believed to be a low productive, oligotrophic marine ecosystem, where the diazotroph communities presumed to play a vital role in adding "new" nitrogen through the nitrogen fixation process. However, the diazotroph communities in the oceanic region of the BoB are still poorly understood though it represents most of the seawater volume. The present study investigated a detailed account of the bacterioplankton community structure and distribution in the oceanic BoB during the winter monsoon using high throughput sequencing targeting the 16S rRNA and nifH genes. Our study observed diverse groups of bacterioplankton communities in the BoB including both cyanobacterial and non-cyanobacterial phylotypes. Cyanobacteria (Prochlorococcus spp. and Synechococcus spp.) and Proteobacteria (mainly α-, γ-, and δ-Proteobacteria) were the most abundant groups within the bacterial communities, possessing differential vertical distribution patterns. Cyanobacteria were more abundant in the surface waters, whereas Proteobacteria dominated the deeper layers (75 m). However, within the diazotroph communities, Proteobacteria (mainly γ-Proteobacteria) were the most dominant groups than Cyanobacteria. Function prediction based on PICRUSt revealed that nitrogen fixation might more active to add fixed nitrogen in the surface waters, while nitrogen removal pathways (denitrification and anammox) might stronger in deeper layers. Canonical correspondence analysis (CCA) indicated that temperature, salinity, and silicate were major environmental factors driving the distribution of bacterial communities. Additionally, phosphate was also an important factor in regulating the diazotroph communities in the surface water. Overall, this study provided detailed information on bacterial communities and their vital role in the nitrogen cycles in oligotrophic ecosystems.
Collapse
Affiliation(s)
- Chao Wu
- Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Dhiraj Dhondiram Narale
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
| | - Zhengguo Cui
- Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Xingzhou Wang
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
- Institute for Advanced Marine Research, China University of Geosciences, Guangzhou, China
| | - Haijiao Liu
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
- Institute for Advanced Marine Research, China University of Geosciences, Guangzhou, China
| | - Wenzhe Xu
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
| | - Guicheng Zhang
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
| | - Jun Sun
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
- Institute for Advanced Marine Research, China University of Geosciences, Guangzhou, China
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, China
| |
Collapse
|
10
|
The marine nitrogen cycle: new developments and global change. Nat Rev Microbiol 2022; 20:401-414. [PMID: 35132241 DOI: 10.1038/s41579-022-00687-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2022] [Indexed: 12/25/2022]
Abstract
The ocean is home to a diverse and metabolically versatile microbial community that performs the complex biochemical transformations that drive the nitrogen cycle, including nitrogen fixation, assimilation, nitrification and nitrogen loss processes. In this Review, we discuss the wealth of new ocean nitrogen cycle research in disciplines from metaproteomics to global biogeochemical modelling and in environments from productive estuaries to the abyssal deep sea. Influential recent discoveries include new microbial functional groups, novel metabolic pathways, original conceptual perspectives and ground-breaking analytical capabilities. These emerging research directions are already contributing to urgent efforts to address the primary challenge facing marine microbiologists today: the unprecedented onslaught of anthropogenic environmental change on marine ecosystems. Ocean warming, acidification, nutrient enrichment and seawater stratification have major effects on the microbial nitrogen cycle, but widespread ocean deoxygenation is perhaps the most consequential for the microorganisms involved in both aerobic and anaerobic nitrogen transformation pathways. In turn, these changes feed back to the global cycles of greenhouse gases such as carbon dioxide and nitrous oxide. At a time when our species casts a lengthening shadow across all marine ecosystems, timely new advances offer us unique opportunities to understand and better predict human impacts on nitrogen biogeochemistry in the changing ocean of the Anthropocene.
Collapse
|
11
|
Suzuki S, Kawachi M, Tsukakoshi C, Nakamura A, Hagino K, Inouye I, Ishida KI. Unstable Relationship Between Braarudosphaera bigelowii (= Chrysochromulina parkeae) and Its Nitrogen-Fixing Endosymbiont. FRONTIERS IN PLANT SCIENCE 2021; 12:749895. [PMID: 34925404 PMCID: PMC8679911 DOI: 10.3389/fpls.2021.749895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
Marine phytoplankton are major primary producers, and their growth is primarily limited by nitrogen in the oligotrophic ocean environment. The haptophyte Braarudosphaera bigelowii possesses a cyanobacterial endosymbiont (UCYN-A), which plays a major role in nitrogen fixation in the ocean. However, host-symbiont interactions are poorly understood because B. bigelowii was unculturable. In this study, we sequenced the complete genome of the B. bigelowii endosymbiont and showed that it was highly reductive and closely related to UCYN-A2 (an ecotype of UCYN-A). We succeeded in establishing B. bigelowii strains and performed microscopic observations. The detailed observations showed that the cyanobacterial endosymbiont was surrounded by a single host derived membrane and divided synchronously with the host cell division. The transcriptome of B. bigelowii revealed that B. bigelowii lacked the expression of many essential genes associated with the uptake of most nitrogen compounds, except ammonia. During cultivation, some of the strains completely lost the endosymbiont. Moreover, we did not find any evidence of endosymbiotic gene transfer from the endosymbiont to the host. These findings illustrate an unstable morphological, metabolic, and genetic relationship between B. bigelowii and its endosymbiont.
Collapse
Affiliation(s)
- Shigekatsu Suzuki
- Biodiversity Division, National Institute for Environmental Studies, Ibaraki, Japan
| | - Masanobu Kawachi
- Biodiversity Division, National Institute for Environmental Studies, Ibaraki, Japan
| | - Chinatsu Tsukakoshi
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Atsushi Nakamura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Kyoko Hagino
- Center for Advanced Marine Core Research, Kochi University, Kochi, Japan
| | - Isao Inouye
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Ken-ichiro Ishida
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| |
Collapse
|
12
|
Li L, Wu C, Huang D, Ding C, Wei Y, Sun J. Integrating Stochastic and Deterministic Process in the Biogeography of N 2-Fixing Cyanobacterium Candidatus Atelocyanobacterium Thalassa. Front Microbiol 2021; 12:654646. [PMID: 34745020 PMCID: PMC8566894 DOI: 10.3389/fmicb.2021.654646] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 09/22/2021] [Indexed: 11/13/2022] Open
Abstract
UCYN-A is one of the most widespread and important marine diazotrophs. Its unusual distribution in both cold/warm and coastal/oceanic waters challenges current understanding about what drives the biogeography of diazotrophs. This study assessed the community assembly processes of the nitrogen-fixing cyanobacterium UCYN-A, developing a framework of assembly processes underpinning the microbial biogeography and diversity. High-throughput sequencing and a qPCR approach targeting the nifH gene were used to investigate three tropical seas: the Bay of Bengal, the Western Pacific Ocean, and the South China Sea. Based on the neutral community model and two types of null models calculating the β-nearest taxon index and the normalized stochasticity ratio, we found that stochastic assembly processes could explain 66-92% of the community assembly; thus, they exert overwhelming influence on UCYN-A biogeography and diversity. Among the deterministic processes, temperature and coastal/oceanic position appeared to be the principal environmental factors driving UCYN-A diversity. In addition, a close linkage between assembly processes and UCYN-A abundance/diversity/drivers can provide clues for the unusual global distribution of UCYN-A.
Collapse
Affiliation(s)
- Liuyang Li
- College of Marine Science and Technology, China University of Geosciences, Wuhan, China.,State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Chao Wu
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China
| | - Danyue Huang
- College of Marine Science and Technology, China University of Geosciences, Wuhan, China.,School of Oceanography, Shanghai Jiao Tong University, Shanghai, China
| | - Changling Ding
- Research Centre for Indian Ocean Ecosystem, Tianjin University of Science and Technology, Tianjin, China.,College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yuqiu Wei
- Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China
| | - Jun Sun
- College of Marine Science and Technology, China University of Geosciences, Wuhan, China
| |
Collapse
|
13
|
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 COMMUNICATIONS 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] [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.
Collapse
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
| |
Collapse
|
14
|
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] [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.
Collapse
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
| |
Collapse
|
15
|
Landa M, Turk-Kubo KA, Cornejo-Castillo FM, Henke BA, Zehr JP. Critical Role of Light in the Growth and Activity of the Marine N 2-Fixing UCYN-A Symbiosis. Front Microbiol 2021; 12:666739. [PMID: 34025621 PMCID: PMC8139342 DOI: 10.3389/fmicb.2021.666739] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/08/2021] [Indexed: 11/27/2022] Open
Abstract
The unicellular N2-fixing cyanobacteria UCYN-A live in symbiosis with haptophytes in the Braarudosphaera bigelowii lineage. Maintaining N2-fixing symbioses between two unicellular partners requires tight coordination of multiple biological processes including cell growth and division and, in the case of the UCYN-A symbiosis, N2 fixation of the symbiont and photosynthesis of the host. In this system, it is thought that the host photosynthesis supports the high energetic cost of N2 fixation, and both processes occur during the light period. However, information on this coordination is very limited and difficult to obtain because the UCYN-A symbiosis has yet to be available in culture. Natural populations containing the UCYN-A2 symbiosis were manipulated to explore the effects of alterations of regular light and dark periods and inhibition of host photosynthesis on N2 fixation (single cell N2 fixation rates), nifH gene transcription, and UCYN-A2 cell division (fluorescent in situ hybridization and nifH gene abundances). The results showed that the light period is critical for maintenance of regular patterns of gene expression, N2 fixation and symbiont replication and cell division. This study suggests a crucial role for the host as a producer of fixed carbon, rather than light itself, in the regulation and implementation of these cellular processes in UCYN-A.
Collapse
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
| |
Collapse
|
16
|
Messer LF, Brown MV, Van Ruth PD, Doubell M, Seymour JR. Temperate southern Australian coastal waters are characterised by surprisingly high rates of nitrogen fixation and diversity of diazotrophs. PeerJ 2021; 9:e10809. [PMID: 33717676 PMCID: PMC7931716 DOI: 10.7717/peerj.10809] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 12/30/2020] [Indexed: 11/20/2022] Open
Abstract
Biological dinitrogen (N2) fixation is one mechanism by which specific microorganisms (diazotrophs) can ameliorate nitrogen (N) limitation. Historically, rates of N2 fixation were believed to be limited outside of the low nutrient tropical and subtropical open ocean; however, emerging evidence suggests that N2 fixation is also a significant process within temperate coastal waters. Using a combination of amplicon sequencing, targeting the nitrogenase reductase gene (nifH), quantitative nifH PCR, and 15N2 stable isotope tracer experiments, we investigated spatial patterns of diazotroph assemblage structure and N2 fixation rates within the temperate coastal waters of southern Australia during Austral autumn and summer. Relative to previous studies in open ocean environments, including tropical northern Australia, and tropical and temperate estuaries, our results indicate that high rates of N2 fixation (10-64 nmol L-1 d-1) can occur within the large inverse estuary Spencer Gulf, while comparatively low rates of N2 fixation (2 nmol L-1 d-1) were observed in the adjacent continental shelf waters. Across the dataset, low concentrations of NO3/NO2 were significantly correlated with the highest N2 fixation rates, suggesting that N2 fixation could be an important source of new N in the region as dissolved inorganic N concentrations are typically limiting. Overall, the underlying diazotrophic community was dominated by nifH sequences from Cluster 1 unicellular cyanobacteria of the UCYN-A clade, as well as non-cyanobacterial diazotrophs related to Pseudomonas stutzeri, and Cluster 3 sulfate-reducing deltaproteobacteria. Diazotroph community composition was significantly influenced by salinity and SiO4 concentrations, reflecting the transition from UCYN-A-dominated assemblages in the continental shelf waters, to Cluster 3-dominated assemblages in the hypersaline waters of the inverse estuary. Diverse, transitional diazotrophic communities, comprised of a mixture of UCYN-A and putative heterotrophic bacteria, were observed at the mouth and southern edge of Spencer Gulf, where the highest N2 fixation rates were observed. In contrast to observations in other environments, no seasonal patterns in N2 fixation rates and diazotroph community structure were apparent. Collectively, our findings are consistent with the emerging view that N2 fixation within temperate coastal waters is a previously overlooked dynamic and potentially important component of the marine N cycle.
Collapse
Affiliation(s)
- Lauren F Messer
- Climate Change Cluster, University of Technology Sydney, Sydney, New South Wales, Australia.,Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD, Australia
| | - Mark V Brown
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales, Australia
| | - Paul D Van Ruth
- Aquatic Sciences, South Australian Research and Development Institute, Adelaide, South Australia, Australia
| | - Mark Doubell
- Aquatic Sciences, South Australian Research and Development Institute, Adelaide, South Australia, Australia
| | - Justin R Seymour
- Climate Change Cluster, University of Technology Sydney, Sydney, New South Wales, Australia
| |
Collapse
|
17
|
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] [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.
Collapse
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
| |
Collapse
|
18
|
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. JOURNAL OF PHYCOLOGY 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] [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.
Collapse
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
| |
Collapse
|
19
|
Liu Y, Lin Q, Feng J, Yang F, Du H, Hu Z, Wang H. Differences in metabolic potential between particle-associated and free-living bacteria along Pearl River Estuary. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 728:138856. [PMID: 32570327 DOI: 10.1016/j.scitotenv.2020.138856] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/15/2020] [Accepted: 04/19/2020] [Indexed: 06/11/2023]
Abstract
Particulate organic matter (POM) in aquatic ecosystem is critical for biogeochemical cycling and host distinct communities of microbes, compared to its surrounding water. In this study, the structures and functional potentials of microbial communities associated with particles or free-living in water samples from the Pearl River Estuary were investigated using 16S rRNA gene sequencing and GeoChip 5.0 analysis. Significant differences in the community structure and genetic functional potentials between particle-associated bacteria and free-living bacteria were observed across all eight sampling sites. In particle-associated bacteria communities, Rhodobacteraceae and Flavobacteriaceae were more abundant, while SAR11 clade and SAR86 clade were the most abundant in free-living bacteria communities. The richness and abundance of functional genes involved in nutrient cycling and stress response, including carbon degradation, nitrogen fixation, DMSP degradation, and polyphosphate degradation, were much higher in particle-associated bacteria compared with free-living bacteria. Thus, the particle-associated bacteria seem to play a much more important role in the biogeochemical cycles than free-living bacteria. In conclusion, the results from this study highlight the central role played by particle-associated bacteria in structuring microbial assemblages, and their importance for mediating biogeochemical cycling in the estuarine ecosystem.
Collapse
Affiliation(s)
- Yanyang Liu
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Qun Lin
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Jiarong Feng
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Fumin Yang
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Hong Du
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Zhong Hu
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China
| | - Hui Wang
- Biology Department, College of Science, Shantou University, Shantou 515063, China; Institute of Marine Sciences, Shantou University, Shantou 515063, China; Guangdong Provincial Key Laboratory of Marine Biotechnology, Shantou University, Shantou 515063, China.
| |
Collapse
|
20
|
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.
Collapse
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
| |
Collapse
|
21
|
Foster RA, Zehr JP. Diversity, Genomics, and Distribution of Phytoplankton-Cyanobacterium Single-Cell Symbiotic Associations. Annu Rev Microbiol 2020; 73:435-456. [PMID: 31500535 DOI: 10.1146/annurev-micro-090817-062650] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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.
Collapse
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;
| |
Collapse
|
22
|
Nieves-Morión M, Flores E, Foster RA. Predicting substrate exchange in marine diatom-heterocystous cyanobacteria symbioses. Environ Microbiol 2020; 22:2027-2052. [PMID: 32281201 DOI: 10.1111/1462-2920.15013] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/02/2020] [Accepted: 04/03/2020] [Indexed: 11/27/2022]
Abstract
In the open ocean, some phytoplankton establish symbiosis with cyanobacteria. Some partnerships involve diatoms as hosts and heterocystous cyanobacteria as symbionts. Heterocysts are specialized cells for nitrogen fixation, and a function of the symbiotic cyanobacteria is to provide the host with nitrogen. However, both partners are photosynthetic and capable of carbon fixation, and the possible metabolites exchanged and mechanisms of transfer are poorly understood. The symbiont cellular location varies from internal to partial to fully external, and this is reflected in the symbiont genome size and content. In order to identify the membrane transporters potentially involved in metabolite exchange, we compare the draft genomes of three differently located symbionts with known transporters mainly from model free-living heterocystous cyanobacteria. The types and numbers of transporters are directly related to the symbiont cellular location: restricted in the endosymbionts and wider in the external symbiont. Three proposed models of metabolite exchange are suggested which take into account the type of transporters in the symbionts and the influence of their cellular location on the available nutrient pools. These models provide a basis for several hypotheses that given the importance of these symbioses in global N and C budgets, warrant future testing.
Collapse
Affiliation(s)
- Mercedes Nieves-Morión
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, 106 91, Sweden
| | - Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 49, Seville, E-41092, Spain
| | - Rachel A Foster
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, 106 91, Sweden
| |
Collapse
|
23
|
Transcriptome reconstruction and functional analysis of eukaryotic marine plankton communities via high-throughput metagenomics and metatranscriptomics. Genome Res 2020; 30:647-659. [PMID: 32205368 PMCID: PMC7197479 DOI: 10.1101/gr.253070.119] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 03/18/2020] [Indexed: 11/25/2022]
Abstract
Large-scale metagenomic and metatranscriptomic data analyses are often restricted by their gene-centric approach, limiting the ability to understand organismal and community biology. De novo assembly of large and mosaic eukaryotic genomes from complex meta-omics data remains a challenging task, especially in comparison with more straightforward bacterial and archaeal systems. Here, we use a transcriptome reconstruction method based on clustering co-abundant genes across a series of metagenomic samples. We investigated the co-abundance patterns of ∼37 million eukaryotic unigenes across 365 metagenomic samples collected during the Tara Oceans expeditions to assess the diversity and functional profiles of marine plankton. We identified ∼12,000 co-abundant gene groups (CAGs), encompassing ∼7 million unigenes, including 924 metagenomics-based transcriptomes (MGTs, CAGs larger than 500 unigenes). We demonstrated the biological validity of the MGT collection by comparing individual MGTs with available references. We identified several key eukaryotic organisms involved in dimethylsulfoniopropionate (DMSP) biosynthesis and catabolism in different oceanic provinces, thus demonstrating the potential of the MGT collection to provide functional insights on eukaryotic plankton. We established the ability of the MGT approach to capture interspecies associations through the analysis of a nitrogen-fixing haptophyte-cyanobacterial symbiotic association. This MGT collection provides a valuable resource for analyses of eukaryotic plankton in the open ocean by giving access to the genomic content and functional potential of many ecologically relevant eukaryotic species.
Collapse
|
24
|
Wu C, Kan J, Liu H, Pujari L, Guo C, Wang X, Sun J. Heterotrophic Bacteria Dominate the Diazotrophic Community in the Eastern Indian Ocean (EIO) during Pre-Southwest Monsoon. MICROBIAL ECOLOGY 2019; 78:804-819. [PMID: 31037377 DOI: 10.1007/s00248-019-01355-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 03/05/2019] [Indexed: 06/09/2023]
Abstract
The diazotrophic communities play an important role in sustaining primary productivity through adding new nitrogen to oligotrophic marine ecosystems. Yet, their composition in the oligotrophic Indian Ocean is poorly understood. Here, we report the first observation of phylogenetic diversity and distribution of diazotrophs in the Eastern Indian Ocean (EIO) surface water (to 200 m) during the pre-southwest monsoon period. Through high throughput sequencing of nifH genes, we identified diverse groups of diazotrophs in the EIO including both non-cyanobacterial and cyanobacterial phylotypes. Proteobacteria (mainly Alpha-, Beta-, and Gamma-proteobacteria) were the most diverse and abundant groups within all the diazotrophs, which accounted for more than 86.9% of the total sequences. Cyanobacteria were also retrieved, and they were dominated by the filamentous non-heterocystous cyanobacteria Trichodesmium spp. Other cyanobacteria such as unicellular diazotrophic cyanobacteria were detected sporadically. Interestingly, our qPCR analysis demonstrated that the depth-integrated gene abundances of the diazotrophic communities exhibited spatial heterogeneity with Trichodesmium spp. appeared to be more abundant in the Bay of Bengal (p < 0.05), while Sagittula castanea (Alphaproteobacteria) was found to be more dominating in the equatorial region and offshores (p < 0.05). Non-metric multidimensional scaling analysis (NMDS) further confirmed distinct vertical and horizontal spatial variations in the EIO. Canonical correspondence analysis (CCA) indicated that temperature, salinity, and phosphate were the major environmental factors driving the distribution of the diazotroph communities. Overall, our study provides the first insight into the diversity and distribution of the diazotrophic communities in EIO. The findings from this study highlight distinct contributions of both non-cyanobacteria and cyanobacteria to N2 fixation. Moreover, our study reveals information that is critical for understanding spatial heterogeneity and distribution of diazotrophs, and their vital roles in nitrogen and carbon cycling.
Collapse
Affiliation(s)
- Chao Wu
- Institute of Marine Science and Technology, Shandong University, Qingdao, 266237, China
| | - Jinjun Kan
- Microbiology Division, Stroud Water Research Center, Avondale, PA, 19311, USA
| | - Haijiao Liu
- Institute of Marine Science and Technology, Shandong University, Qingdao, 266237, China
| | - Laxman Pujari
- Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin, 300457, China
- Research Centre for Indian Ocean Ecosystem, Tianjin University of science and Technology, Tianjin, 300457, China
| | - Congcong Guo
- Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin, 300457, China
- Research Centre for Indian Ocean Ecosystem, Tianjin University of science and Technology, Tianjin, 300457, China
| | - Xingzhou Wang
- Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin, 300457, China
- Research Centre for Indian Ocean Ecosystem, Tianjin University of science and Technology, Tianjin, 300457, China
| | - Jun Sun
- Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin, 300457, China.
- Research Centre for Indian Ocean Ecosystem, Tianjin University of science and Technology, Tianjin, 300457, China.
- College of Marine & Environmental Sciences, Tianjin University of Science and Technology, No.29 13th Avenue, TEDA, Tianjin, 300457, People's Republic of China.
| |
Collapse
|
25
|
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] [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.
Collapse
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
| | | |
Collapse
|
26
|
Abstract
Biological dinitrogen (N2) fixation (BNF) is an important source of nitrogen in marine systems. Until recently, it was believed to be primarily limited to subtropical open oceans. Marine BNF is mainly attributed to cyanobacteria. However, recently an unusual N2-fixing unicellular cyanobacteria (UCYN-A)/haptophyte symbiosis was reported with a broader temperature range than other N2-fixing cyanobacteria. We report that the UCYN-A symbiosis is present and fixing N2 in the Western Arctic and Bering Seas, further north than any previously reported N2-fixing marine cyanobacteria. Nanoscale secondary ion mass spectrometry enabled us to directly show that the symbiosis was fixing N2. These results show that N2-fixing cyanobacteria are not constrained to subtropical waters and challenge commonly held ideas about global marine N2 fixation. Biological dinitrogen (N2) fixation is an important source of nitrogen (N) in low-latitude open oceans. The unusual N2-fixing unicellular cyanobacteria (UCYN-A)/haptophyte symbiosis has been found in an increasing number of unexpected environments, including northern waters of the Danish Straight and Bering and Chukchi Seas. We used nanoscale secondary ion mass spectrometry (nanoSIMS) to measure 15N2 uptake into UCYN-A/haptophyte symbiosis and found that UCYN-A strains identical to low-latitude strains are fixing N2 in the Bering and Chukchi Seas, at rates comparable to subtropical waters. These results show definitively that cyanobacterial N2 fixation is not constrained to subtropical waters, challenging paradigms and models of global N2 fixation. The Arctic is particularly sensitive to climate change, and N2 fixation may increase in Arctic waters under future climate scenarios.
Collapse
|
27
|
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] [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.
Collapse
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
| |
Collapse
|
28
|
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 JOURNAL 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] [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.
Collapse
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
| |
Collapse
|
29
|
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] [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.
Collapse
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
| |
Collapse
|
30
|
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] [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.
Collapse
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
| |
Collapse
|
31
|
Small eukaryotic phytoplankton communities in tropical waters off Brazil are dominated by symbioses between Haptophyta and nitrogen-fixing cyanobacteria. ISME JOURNAL 2018; 12:1360-1374. [PMID: 29426951 DOI: 10.1038/s41396-018-0050-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 11/01/2017] [Accepted: 12/20/2017] [Indexed: 01/09/2023]
Abstract
Symbioses between eukaryotic algae and nitrogen-fixing cyanobacteria have been recognized in recent years as a key source of new nitrogen in the oceans. We investigated the composition of the small photosynthetic eukaryote communities associated with nitrogen-fixing cyanobacteria in the Brazilian South Atlantic Bight using a combination of flow cytometry sorting and high throughput sequencing of two genes: the V4 region of 18S rRNA and nifH. Two distinct eukaryotic communities were often encountered, one dominated by the Mamiellophyceae Bathycoccus and Ostreococcus, and one dominated by a prymnesiophyte known to live in symbiosis with the UCYN-A1 nitrogen-fixing cyanobacterium. Among nifH sequences, those from UCYN-A1 were most abundant but three other UCYN-A clades (A2, A3, A4) were also found. Network analysis confirmed the relation between A1 and A2 clades and their hypothesized hosts and pointed out to the potential association between novel clade A4 with Braarudosphaera bigelowii, previously hypothesized to host A2.
Collapse
|
32
|
Cheung S, Suzuki K, Saito H, Umezawa Y, Xia X, Liu H. Highly heterogeneous diazotroph communities in the Kuroshio Current and the Tokara Strait, Japan. PLoS One 2017; 12:e0186875. [PMID: 29059241 PMCID: PMC5653367 DOI: 10.1371/journal.pone.0186875] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 10/09/2017] [Indexed: 11/18/2022] Open
Abstract
In this study, we used 454-pyrosequencing to report the highly diverse diazotroph communities in the Kuroshio and its adjacent waters along a transect across the Tokara Strait, Japan. Terrestrial input from the islands resulted in a highly heterogeneous diazotroph community within a relatively small geographic region, which was presumably caused by the remarkably different responses of UCYN-A2, UCYN-C and Trichodesmium to the steep environmental gradient. On the other hand, most major cyanobacterial OTUs found in this study were also detected in an unpublished dataset from the upstream Kuroshio, which suggests transportation of diazotrophs by the Kuroshio in large geographic scale. A significant amount of UCYN-C was found in the Kuroshio and offshore stations, suggesting the importance of this potentially overlooked group in the western North Pacific Ocean (WNPO). Moreover, a novel sublineage of UCYN-B was defined, which was predominant in an oligotrophic water sample; and it was also found to be widely distributed in oceanic waters. In addition, the apparent increase in relative abundance of UCYN-A2 from offshore to near-shore water provides evidence for the earlier and under-debating view that UCYN-A2 prefers coastal conditions. Our report provides new knowledge for understanding the phylogeny and ecology of unicellular cyanobacterial diazotrophs in WNPO.
Collapse
Affiliation(s)
- Shunyan Cheung
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Koji Suzuki
- Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan
| | - Hiroaki Saito
- Atmosphere and Ocean Research Institute, The University of Tokyo, Tokyo, Japan
| | - Yu Umezawa
- Faculty of Fisheries, Nagasaki University, Nagasaki, Japan
| | - Xiaomin Xia
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Hongbin Liu
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong, China
| |
Collapse
|