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Vipindas PV, Venkatachalam S, Jabir T, Yang EJ, Jung J, Jain A, Krishnan KP. Salinity-controlled distribution of prokaryotic communities in the Arctic sea-ice melt ponds. World J Microbiol Biotechnol 2023; 40:25. [PMID: 38057653 DOI: 10.1007/s11274-023-03850-7] [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: 08/28/2023] [Accepted: 11/22/2023] [Indexed: 12/08/2023]
Abstract
The thawing of snow and sea ice produces distinctive melt ponds on the surface of the Arctic sea ice, which covers a significant portion of the surface sea ice during summer. Melt-pond salinity impacts heat transfer to the ice below and the melting rate. It is widely known that melt ponds play a significant role in heat fluxes, ice-albedo feedback, and sea-ice energy balance. However, not much attention has been given to the fact that melt ponds also serve as a unique microbial ecosystem where microbial production begins as soon as they are formed. Here, we investigated the role of melt pond salinity in controlling the diversity and distribution of prokaryotic communities using culture-dependent and -independent approaches. The 16 S rRNA gene amplicon based next generation sequencing analysis retrieved a total of 14 bacterial phyla, consisting of 146 genera, in addition to two archaeal phyla. Further, the culture-dependent approaches of the study allowed for the isolation and identification of twenty-four bacterial genera in pure culture. Flavobacterium, Candidatus_Aquiluna, SAR11 clade, Polaribacter, Glaciecola, and Nonlabens were the dominant genera observed in the amplicon analysis. Whereas Actimicrobium, Rhodoglobus, Flavobacterium, and Pseudomonas were dominated in the culturable fraction. Our results also demonstrated that salinity, chlorophyll a, and dissolved organic carbon were the significant environmental variables controlling the prokaryotic community distribution in melt ponds. A significant community shift was observed in melt ponds when the salinity changed with the progression of melting and deepening of ponds. Different communities were found to be dominant in melt ponds with different salinity ranges. It was also observed that melt pond prokaryotic communities significantly differed from the surface ocean microbial community. Our observations suggest that complex prokaryotic communities develop in melt ponds immediately after its formation using dissolved organic carbon generated through primary production in the oligotrophic water.
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Affiliation(s)
- Puthiya Veettil Vipindas
- Arctic Ecology and Biogeochemistry Division, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa, 403 804, India.
| | - Siddarthan Venkatachalam
- Arctic Ecology and Biogeochemistry Division, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa, 403 804, India
| | - Thajudeen Jabir
- Arctic Ecology and Biogeochemistry Division, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa, 403 804, India
| | - Eun Jin Yang
- Division of Polar Ocean Sciences, Korea Polar Research Institute, 26 Songdo-dong, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - Jinyoung Jung
- Division of Polar Ocean Sciences, Korea Polar Research Institute, 26 Songdo-dong, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - Anand Jain
- Arctic Ecology and Biogeochemistry Division, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa, 403 804, India
| | - Kottekkatu Padinchati Krishnan
- Arctic Ecology and Biogeochemistry Division, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco-da-Gama, Goa, 403 804, India
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2
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Robicheau BM, Tolman J, Rose S, Desai D, LaRoche J. Marine nitrogen-fixers in the Canadian Arctic Gateway are dominated by biogeographically distinct noncyanobacterial communities. FEMS Microbiol Ecol 2023; 99:fiad122. [PMID: 37951299 PMCID: PMC10656255 DOI: 10.1093/femsec/fiad122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 07/30/2023] [Accepted: 11/09/2023] [Indexed: 11/13/2023] Open
Abstract
We describe diazotrophs present during a 2015 GEOTRACES expedition through the Canadian Arctic Gateway (CAG) using nifH metabarcoding. In the less studied Labrador Sea, Bradyrhizobium sp. and Vitreoscilla sp. nifH variants were dominant, while in Baffin Bay, a Stutzerimonas stutzeri variant was dominant. In comparison, the Canadian Arctic Archipelago (CAA) was characterized by a broader set of dominant variants belonging to Desulfobulbaceae, Desulfuromonadales, Arcobacter sp., Vibrio spp., and Sulfuriferula sp. Although dominant diazotrophs fell within known nifH clusters I and III, only a few of these variants were frequently recovered in a 5-year weekly nifH times series in the coastal NW Atlantic presented herein, notably S. stutzeri and variants belonging to Desulfobacterales and Desulfuromonadales. In addition, the majority of dominant Arctic nifH variants shared low similarity (< 92% nucleotide identities) to sequences in a global noncyanobacterial diazotroph catalog recently compiled by others. We further detected UCYN-A throughout the CAG at low-levels using quantitative-PCR assays. Temperature, depth, salinity, oxygen, and nitrate were most strongly correlated to the Arctic diazotroph diversity observed, and we found a stark division between diazotroph communities of the Labrador Sea versus Baffin Bay and the CAA, hence establishing that a previously unknown biogeographic community division can occur for diazotrophs in the CAG.
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Affiliation(s)
- Brent M Robicheau
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Jennifer Tolman
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Sonja Rose
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Dhwani Desai
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
- Department of Pharmacology, Dalhousie University, 5850 College Street, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Julie LaRoche
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada
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3
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Turk-Kubo KA, Gradoville MR, Cheung S, Cornejo-Castillo FM, Harding KJ, Morando M, Mills M, Zehr JP. Non-cyanobacterial diazotrophs: global diversity, distribution, ecophysiology, and activity in marine waters. FEMS Microbiol Rev 2023; 47:fuac046. [PMID: 36416813 PMCID: PMC10719068 DOI: 10.1093/femsre/fuac046] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/15/2022] [Accepted: 11/17/2022] [Indexed: 12/17/2023] Open
Abstract
Biological dinitrogen (N2) fixation supplies nitrogen to the oceans, supporting primary productivity, and is carried out by some bacteria and archaea referred to as diazotrophs. Cyanobacteria are conventionally considered to be the major contributors to marine N2 fixation, but non-cyanobacterial diazotrophs (NCDs) have been shown to be distributed throughout ocean ecosystems. However, the biogeochemical significance of marine NCDs has not been demonstrated. This review synthesizes multiple datasets, drawing from cultivation-independent molecular techniques and data from extensive oceanic expeditions, to provide a comprehensive view into the diversity, biogeography, ecophysiology, and activity of marine NCDs. A NCD nifH gene catalog was compiled containing sequences from both PCR-based and PCR-free methods, identifying taxa for future studies. NCD abundances from a novel database of NCD nifH-based abundances were colocalized with environmental data, unveiling distinct distributions and environmental drivers of individual taxa. Mechanisms that NCDs may use to fuel and regulate N2 fixation in response to oxygen and fixed nitrogen availability are discussed, based on a metabolic analysis of recently available Tara Oceans expedition data. The integration of multiple datasets provides a new perspective that enhances understanding of the biology, ecology, and biogeography of marine NCDs and provides tools and directions for future research.
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Affiliation(s)
- Kendra A Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Mary R Gradoville
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Columbia River Inter-Tribal Fish Commission, Portland, OR, United States
| | - Shunyan Cheung
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Francisco M Cornejo-Castillo
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM-CSIC), Pg. Marítim Barceloneta, 37-49 08003 Barcelona, Spain
| | - Katie J Harding
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
- Marine Biology Research Division, Scripps Institute of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - Michael Morando
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
| | - Matthew Mills
- Department of Earth System Science, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
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Jabir T, Jain A, Vipindas PV, Krishnan KP. Stochastic Processes Dominate in the Water Mass-Based Segregation of Diazotrophs in a High Arctic Fjord (Svalbard). MICROBIAL ECOLOGY 2023; 86:2733-2746. [PMID: 37532947 DOI: 10.1007/s00248-023-02276-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 07/24/2023] [Indexed: 08/04/2023]
Abstract
Nitrogen-fixing or diazotrophic microbes fix atmospheric nitrogen (N2) to ammonia (NH3+) using nitrogenase enzyme and play a crucial role in regulating marine primary productivity and carbon dioxide sequestration. However, there is a lack of information about the diversity, structure, and environmental regulations of the diazotrophic communities in the high Arctic fjords, such as Kongsfjorden. Here, we employed nifH gene sequencing to clarify variations in composition, community structure, and assembly mechanism among the diazotrophs of the salinity-driven stratified waters of Kongsfjorden. The principal environmental and ecological drivers of the observed variations were identified. The majority of the nifH gene sequences obtained in the present study belonged to cluster I and cluster III nifH phylotypes, accounting for 65% and 25% of the total nifH gene sequences. The nifH gene diversity and composition, irrespective of the size fractions (free-living and particle attached), showed a clear separation among water mass types, i.e., Atlantic-influenced versus glacier-influenced water mass. Higher nifH gene diversity and relative abundances of non-cyanobacterial nifH OTUs, affiliated with uncultured Rhizobiales, Burkholderiales, Alteromonadaceae, Gallionellaceae (cluster I) and uncultured Deltaproteobacteria including Desulfuromonadaceae (cluster III), were prevalent in GIW while uncultured Gammaproteobacteria and Desulfobulbaceae were abundant in AIW. The diazotrophic community assembly was dominated by stochastic processes, principally ecological drift, and to lesser degrees dispersal limitation and homogeneous dispersal. Differences in the salinity and dissolved oxygen content lead to the vertical segregation of diazotrophs among water mass types. These findings suggest that water column stratification affects the composition and assembly mechanism of diazotrophic communities and thus could affect nitrogen fixation in the Arctic fjord.
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Affiliation(s)
- Thajudeen Jabir
- Arctic Ecology and Biogeochemistry, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco da Gama, Goa, 403 804, India.
| | - Anand Jain
- Arctic Ecology and Biogeochemistry, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco da Gama, Goa, 403 804, India
| | - Puthiya Veettil Vipindas
- Arctic Ecology and Biogeochemistry, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco da Gama, Goa, 403 804, India
| | - Kottekkatu Padinchati Krishnan
- Arctic Ecology and Biogeochemistry, National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco da Gama, Goa, 403 804, India
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5
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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.
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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
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6
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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.
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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
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7
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Alcamán-Arias ME, Cifuentes-Anticevic J, Castillo-Inaipil W, Farías L, Sanhueza C, Fernández-Gómez B, Verdugo J, Abarzua L, Ridley C, Tamayo-Leiva J, Díez B. Dark Diazotrophy during the Late Summer in Surface Waters of Chile Bay, West Antarctic Peninsula. Microorganisms 2022; 10:microorganisms10061140. [PMID: 35744658 PMCID: PMC9227844 DOI: 10.3390/microorganisms10061140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 05/28/2022] [Accepted: 05/29/2022] [Indexed: 11/16/2022] Open
Abstract
Although crucial for the addition of new nitrogen in marine ecosystems, dinitrogen (N2) fixation remains an understudied process, especially under dark conditions and in polar coastal areas, such as the West Antarctic Peninsula (WAP). New measurements of light and dark N2 fixation rates in parallel with carbon (C) fixation rates, as well as analysis of the genetic marker nifH for diazotrophic organisms, were conducted during the late summer in the coastal waters of Chile Bay, South Shetland Islands, WAP. During six late summers (February 2013 to 2019), Chile Bay was characterized by high NO3− concentrations (~20 µM) and an NH4+ content that remained stable near 0.5 µM. The N:P ratio was approximately 14.1, thus close to that of the Redfield ratio (16:1). The presence of Cluster I and Cluster III nifH gene sequences closely related to Alpha-, Delta- and, to a lesser extent, Gammaproteobacteria, suggests that chemosynthetic and heterotrophic bacteria are primarily responsible for N2 fixation in the bay. Photosynthetic carbon assimilation ranged from 51.18 to 1471 nmol C L−1 d−1, while dark chemosynthesis ranged from 9.24 to 805 nmol C L−1 d−1. N2 fixation rates were higher under dark conditions (up to 45.40 nmol N L−1 d−1) than under light conditions (up to 7.70 nmol N L−1 d−1), possibly contributing more than 37% to new nitrogen-based production (≥2.5 g N m−2 y−1). Of all the environmental factors measured, only PO43- exhibited a significant correlation with C and N2 rates, being negatively correlated (p < 0.05) with dark chemosynthesis and N2 fixation under the light condition, revealing the importance of the N:P ratio for these processes in Chile Bay. This significant contribution of N2 fixation expands the ubiquity and biological potential of these marine chemosynthetic diazotrophs. As such, this process should be considered along with the entire N cycle when further reviewing highly productive Antarctic coastal waters and the diazotrophic potential of the global marine ecosystem.
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Affiliation(s)
- María E. Alcamán-Arias
- Departamento de Oceanografía, Universidad de Concepción, Concepción 4030000, Chile; (M.E.A.-A.); (L.F.); (L.A.)
- Center for Climate and Resilience Research (CR)2, Universidad de Chile, Blanco Encalada 2002, Santiago 8320000, Chile; (C.R.); (J.T.-L.)
- Escuela de Medicina, Universidad Espíritu Santo, Guayaquil 0901952, Ecuador
| | - Jerónimo Cifuentes-Anticevic
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
| | - Wilson Castillo-Inaipil
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
| | - Laura Farías
- Departamento de Oceanografía, Universidad de Concepción, Concepción 4030000, Chile; (M.E.A.-A.); (L.F.); (L.A.)
- Center for Climate and Resilience Research (CR)2, Universidad de Chile, Blanco Encalada 2002, Santiago 8320000, Chile; (C.R.); (J.T.-L.)
| | - Cynthia Sanhueza
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
| | - Beatriz Fernández-Gómez
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
- Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria (ULPGC), 35001 Las Palmas, Spain
| | - Josefa Verdugo
- Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany;
| | - Leslie Abarzua
- Departamento de Oceanografía, Universidad de Concepción, Concepción 4030000, Chile; (M.E.A.-A.); (L.F.); (L.A.)
| | - Christina Ridley
- Center for Climate and Resilience Research (CR)2, Universidad de Chile, Blanco Encalada 2002, Santiago 8320000, Chile; (C.R.); (J.T.-L.)
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
| | - Javier Tamayo-Leiva
- Center for Climate and Resilience Research (CR)2, Universidad de Chile, Blanco Encalada 2002, Santiago 8320000, Chile; (C.R.); (J.T.-L.)
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
- Center for Genome Regulation (CRG), Universidad de Chile, Blanco Encalada 2085, Santiago 8320000, Chile
| | - Beatriz Díez
- Center for Climate and Resilience Research (CR)2, Universidad de Chile, Blanco Encalada 2002, Santiago 8320000, Chile; (C.R.); (J.T.-L.)
- Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; (J.C.-A.); (W.C.-I.); (C.S.); (B.F.-G.)
- Center for Genome Regulation (CRG), Universidad de Chile, Blanco Encalada 2085, Santiago 8320000, Chile
- Correspondence:
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Li W, Li F, Zeng H, Ma L, Qi L, Wang X, Wang W, Peng Z, Degen AA, Bai Y, Zhang T, Huang M, Han J, Shang Z. Diversity and Variation of Asymbiotic Nitrogen-Fixing Microorganisms in Alpine Grasslands on the Tibetan Plateau. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.702848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Asymbiotic nitrogen-fixing (ANF) bacteria contribute a substantial amount of nitrogen in ecosystems, especially in those with low symbiotic nitrogen fixation (SNF) capability. Degradation of alpine grassland is widespread on the Tibetan Plateau and sown grassland has become one of the main strategies for grassland restoration. However, the diversity and community structure of ANF bacteria in different grassland types remain unknown. The aim of this study was to fill this gap. Soil samples were obtained from 39 grassland plots selected from three counties in the eastern Tibetan Plateau. The plots were classified as natural grassland (NG), sown grassland (SG), lightly degraded grassland (LDG), and severely degraded grassland (SDG). ANF microbial communities of the four grassland types were compared at the level of community and species diversity by 16S rRNA high-throughput sequencing technology. The phylum Proteobacteria accounted for >72% of the ANF bacteria. The community structures of soil ANF bacteria differed significantly (p < 0.01) among grassland types. We concluded that: (1) planting gramineous forage could possibly mitigate the decrease in diversity of soil ANF bacteria caused by grassland degradation; and (2) the diversity of soil ANF bacteria in alpine grassland of the Tibetan Plateau is closely related to grassland degradation and restoration.
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9
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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.
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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
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10
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Kapili BJ, Dekas AE. PPIT: an R package for inferring microbial taxonomy from nifH sequences. Bioinformatics 2021; 37:2289-2298. [PMID: 33580675 DOI: 10.1093/bioinformatics/btab100] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/22/2020] [Accepted: 02/11/2021] [Indexed: 11/14/2022] Open
Abstract
MOTIVATION Linking microbial community members to their ecological functions is a central goal of environmental microbiology. When assigned taxonomy, amplicon sequences of metabolic marker genes can suggest such links, thereby offering an overview of the phylogenetic structure underpinning particular ecosystem functions. However, inferring microbial taxonomy from metabolic marker gene sequences remains a challenge, particularly for the frequently sequenced nitrogen fixation marker gene, nitrogenase reductase (nifH). Horizontal gene transfer in recent nifH evolutionary history can confound taxonomic inferences drawn from the pairwise identity methods used in existing software. Other methods for inferring taxonomy are not standardized and require manual inspection that is difficult to scale. RESULTS We present Phylogenetic Placement for Inferring Taxonomy (PPIT), an R package that infers microbial taxonomy from nifH amplicons using both phylogenetic and sequence identity approaches. After users place query sequences on a reference nifH gene tree provided by PPIT (n = 6317 full-length nifH sequences), PPIT searches the phylogenetic neighborhood of each query sequence and attempts to infer microbial taxonomy. An inference is drawn only if references in the phylogenetic neighborhood are: (1) taxonomically consistent and (2) share sufficient pairwise identity with the query, thereby avoiding erroneous inferences due to known horizontal gene transfer events. We find that PPIT returns a higher proportion of correct taxonomic inferences than BLAST-based approaches at the cost of fewer total inferences. We demonstrate PPIT on deep-sea sediment and find that Deltaproteobacteria are the most abundant potential diazotrophs. Using this dataset we show that emending PPIT inferences based on visual inspection of query sequence placement can achieve taxonomic inferences for nearly all sequences in a query set. We additionally discuss how users can apply PPIT to the analysis of other marker genes. AVAILABILITY PPIT is freely available to non-commercial users at https://github.com/bkapili/ppit. Installation includes a vignette that demonstrates package use and reproduces the nifH amplicon analysis discussed here. The raw nifH amplicon sequence data have been deposited in the GenBank, EMBL, and DDBJ databases under BioProject number PRJEB37167. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Bennett J Kapili
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Anne E Dekas
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
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11
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Jabir T, Vipindas PV, Krishnan KP, Mohamed Hatha AA. Abundance and diversity of diazotrophs in the surface sediments of Kongsfjorden, an Arctic fjord. World J Microbiol Biotechnol 2021; 37:41. [PMID: 33544264 DOI: 10.1007/s11274-020-02993-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/27/2020] [Indexed: 10/22/2022]
Abstract
Diazotrophy in the Arctic environment is poorly understood compared to tropical and subtropical regions. Hence in this study, we report the abundance and diversity of diazotrophs in Arctic fjord sediments and elucidate the role of environmental factors on the distribution of diazotrophs. The study was conducted during the boreal summer in the Kongsfjorden, an Arctic fjord situated in the western coast of Spitsbergen. The abundance of nifH gene was measured through quantitative real-time PCR and the diversity of diazotrophs was assessed by nifH targeted clone library and next generation sequence analysis. Results revealed that the abundance of nifH gene in the surface sediments ranged from 2.3 × 106 to 3.7 × 107 copies g- 1. The δ-proteobacterial diazotrophs (71% of total sequence) were the dominant class observed in this study. Major genera retrieved from the sequence analysis were Desulfovibrionaceae (25% of total sequence), Desulfuromonadaceae (18% of total sequence) and Desulfobacteriaceae (10% of total sequence); these are important diazotrophic iron and sulfur-reducing bacterial clade in the Kongsfjorden sediments. The abundance of nifH gene showed a significant positive correlation TOC/TN ratio (r2 = 0.96, p ≤ 0.05) and total organic carbon (p ≤ 0.05) content in the fjord sediments. The higher TOC/TN ratio (4.24-14.5) indicated low nitrogen content organic matter in the fjord sediments through glacier runoff, which enhances the abundance and diversity of nitrogen fixing microorganisms.
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Affiliation(s)
- T Jabir
- National Centre for Polar and Ocean Research, Ministry of Earth Sciences (Government of India), Headland Sada, Vasco-da-Gama, Goa, 403 804, India
| | - P V Vipindas
- National Centre for Polar and Ocean Research, Ministry of Earth Sciences (Government of India), Headland Sada, Vasco-da-Gama, Goa, 403 804, India
| | - K P Krishnan
- National Centre for Polar and Ocean Research, Ministry of Earth Sciences (Government of India), Headland Sada, Vasco-da-Gama, Goa, 403 804, India. .,CUSAT-NCPOR Centre for Polar Sciences, Cochin University of Science and Technology (CUSAT), Kochi, 682 016, India.
| | - A A Mohamed Hatha
- Department of Marine Biology, Microbiology, Biochemistry, School of Marine Sciences, Cochin University of Science and Technology (CUSAT), Kochi, 682 016, India.,CUSAT-NCPOR Centre for Polar Sciences, Cochin University of Science and Technology (CUSAT), Kochi, 682 016, India
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12
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von Friesen LW, Riemann L. Nitrogen Fixation in a Changing Arctic Ocean: An Overlooked Source of Nitrogen? Front Microbiol 2021; 11:596426. [PMID: 33391213 PMCID: PMC7775723 DOI: 10.3389/fmicb.2020.596426] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/17/2020] [Indexed: 11/13/2022] Open
Abstract
The Arctic Ocean is the smallest ocean on Earth, yet estimated to play a substantial role as a global carbon sink. As climate change is rapidly changing fundamental components of the Arctic, it is of local and global importance to understand and predict consequences for its carbon dynamics. Primary production in the Arctic Ocean is often nitrogen-limited, and this is predicted to increase in some regions. It is therefore of critical interest that biological nitrogen fixation, a process where some bacteria and archaea termed diazotrophs convert nitrogen gas to bioavailable ammonia, has now been detected in the Arctic Ocean. Several studies report diverse and active diazotrophs on various temporal and spatial scales across the Arctic Ocean. Their ecology and biogeochemical impact remain poorly known, and nitrogen fixation is so far absent from models of primary production in the Arctic Ocean. The composition of the diazotroph community appears distinct from other oceans – challenging paradigms of function and regulation of nitrogen fixation. There is evidence of both symbiotic cyanobacterial nitrogen fixation and heterotrophic diazotrophy, but large regions are not yet sampled, and the sparse quantitative data hamper conclusive insights. Hence, it remains to be determined to what extent nitrogen fixation represents a hitherto overlooked source of new nitrogen to consider when predicting future productivity of the Arctic Ocean. Here, we discuss current knowledge on diazotroph distribution, composition, and activity in pelagic and sea ice-associated environments of the Arctic Ocean. Based on this, we identify gaps and outline pertinent research questions in the context of a climate change-influenced Arctic Ocean – with the aim of guiding and encouraging future research on nitrogen fixation in this region.
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Affiliation(s)
- Lisa W von Friesen
- Marine Biology Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
| | - Lasse Riemann
- Marine Biology Section, Department of Biology, University of Copenhagen, Helsingør, Denmark
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13
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Lee TK, Han I, Kim MS, Seong HJ, Kim JS, Sul WJ. Characterization of a nifH-Harboring Bacterial Community in the Soil-Limited Gotjawal Forest. Front Microbiol 2019; 10:1858. [PMID: 31456776 PMCID: PMC6700220 DOI: 10.3389/fmicb.2019.01858] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 07/29/2019] [Indexed: 11/13/2022] Open
Abstract
Using a high-throughput metagenomic approach, we evaluated nifH-harboring bacterial communities and their assembly in the Gotjawal forest, which was naturally formed on basalt rocks with thin layer of soil. Significant differences in soil properties and community structure were observed in comparison with similar communities in various habitats, including other lava-formed forests (on Jeju Island and in Hawaii) and in regions with high humidity (Florida) or low temperatures (Alaska). nifH-harboring bacterial communities were found to assemble along gradients of environmental factors, particularly cation-exchange capacity. Unlike in other regions, in the Gotjawal forest, Paenibacillus and Clostridium, which belong to the phylum Firmicutes, were present in significantly higher proportion than in other regions. Network analysis suggested that much fewer co-occurrence relationships occurred in the Gotjawal forest than in other lava-formed forests. Our results indicate that the unique nifH-harboring bacterial community and its assembly in the Gotjawal forest are due to its distinctive soil properties, which has implications for microbial interactions and functional potentials.
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Affiliation(s)
- Tae Kwon Lee
- Department of Environmental Engineering, Yonsei University, Wonju, South Korea
| | - Il Han
- Department of Environmental Engineering, Yonsei University, Wonju, South Korea
| | - Min Sung Kim
- Department of Environmental Engineering, Yonsei University, Wonju, South Korea
| | - Hoon Je Seong
- Department of Systems Biotechnology, Chung-Ang University, Anseong, South Korea
| | - Jong-Shik Kim
- Marine Industry Research Institute for East Sea Rim, Uljin, South Korea
| | - Woo Jun Sul
- Department of Systems Biotechnology, Chung-Ang University, Anseong, South Korea
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14
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Zeppenfeld S, van Pinxteren M, Hartmann M, Bracher A, Stratmann F, Herrmann H. Glucose as a Potential Chemical Marker for Ice Nucleating Activity in Arctic Seawater and Melt Pond Samples. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8747-8756. [PMID: 31248257 DOI: 10.1021/acs.est.9b01469] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Recent studies pointed to a high ice nucleating activity (INA) in the Arctic sea surface microlayer (SML). However, related chemical information is still sparse. In the present study, INA and free glucose concentrations were quantified in Arctic SML and bulk water samples from the marginal ice zone, the ice-free ocean, melt ponds, and open waters within the ice pack. T50 (defining INA) ranged from -17.4 to -26.8 °C. Glucose concentrations varied from 0.6 to 51 μg/L with highest values in the SML from the marginal ice zone and melt ponds (median 16.3 and 13.5 μg/L) and lower values in the SML from the ice pack and the ice-free ocean (median 3.9 and 4.0 μg/L). Enrichment factors between the SML and the bulk ranged from 0.4 to 17. A positive correlation was observed between free glucose concentration and INA in Arctic water samples (T50(°C) = (-25.6 ± 0.6) + (0.15 ± 0.04)·Glucose(μg/L), RP = 0.66, n = 74). Clustering water samples based on phytoplankton pigment composition resulted in robust but different correlations within the four clusters (RP between 0.67 and 0.96), indicating a strong link to phytoplankton-related processes. Since glucose did not show significant INA itself, free glucose may serve as a potential tracer for INA in Arctic water samples.
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Affiliation(s)
| | | | | | - Astrid Bracher
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research , Bremerhaven , Germany
- Institute of Environmental Physics , University of Bremen , Bremen , Germany
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15
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de Sousa AGG, Tomasino MP, Duarte P, Fernández-Méndez M, Assmy P, Ribeiro H, Surkont J, Leite RB, Pereira-Leal JB, Torgo L, Magalhães C. Diversity and Composition of Pelagic Prokaryotic and Protist Communities in a Thin Arctic Sea-Ice Regime. MICROBIAL ECOLOGY 2019; 78:388-408. [PMID: 30623212 DOI: 10.1007/s00248-018-01314-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 12/25/2018] [Indexed: 06/09/2023]
Abstract
One of the most prominent manifestations of climate change is the changing Arctic sea-ice regime with a reduction in the summer sea-ice extent and a shift from thicker, perennial multiyear ice towards thinner, first-year ice. These changes in the physical environment are likely to impact microbial communities, a key component of Arctic marine food webs and biogeochemical cycles. During the Norwegian young sea ICE expedition (N-ICE2015) north of Svalbard, seawater samples were collected at the surface (5 m), subsurface (20 or 50 m), and mesopelagic (250 m) depths on 9 March, 27 April, and 16 June 2015. In addition, several physical and biogeochemical data were recorded to contextualize the collected microbial communities. Through the massively parallel sequencing of the small subunit ribosomal RNA amplicon and metagenomic data, this work allows studying the Arctic's microbial community structure during the late winter to early summer transition. Results showed that, at compositional level, Alpha- (30.7%) and Gammaproteobacteria (28.6%) are the most frequent taxa across the prokaryotic N-ICE2015 collection, and also the most phylogenetically diverse. Winter to early summer trends were quite evident since there was a high relative abundance of thaumarchaeotes in the under-ice water column in late winter while this group was nearly absent during early summer. Moreover, the emergence of Flavobacteria and the SAR92 clade in early summer might be associated with the degradation of a spring bloom of Phaeocystis. High relative abundance of hydrocarbonoclastic bacteria, particularly Alcanivorax (54.3%) and Marinobacter (6.3%), was also found. Richness showed different patterns along the depth gradient for prokaryotic (highest at mesopelagic depth) and protistan communities (higher at subsurface depths). The microbial N-ICE2015 collection analyzed in the present study provides comprehensive new knowledge about the pelagic microbiota below drifting Arctic sea-ice. The higher microbial diversity found in late winter/early spring communities reinforces the need to continue with further studies to properly characterize the winter microbial communities under the pack-ice.
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Affiliation(s)
- António Gaspar G de Sousa
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Porto, Portugal.
- Department of Biology, Faculty of Sciences, University of Porto, Rua Campo Alegre s/n, 4169-007, Porto, Portugal.
| | - Maria Paola Tomasino
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Porto, Portugal
| | - Pedro Duarte
- Norwegian Polar Institute, Fram Centre, N-9296, Tromsø, Norway
| | | | - Philipp Assmy
- Norwegian Polar Institute, Fram Centre, N-9296, Tromsø, Norway
| | - Hugo Ribeiro
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Porto, Portugal
| | - Jaroslaw Surkont
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156, Oeiras, Portugal
| | - Ricardo B Leite
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156, Oeiras, Portugal
| | - José B Pereira-Leal
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156, Oeiras, Portugal
| | - Luís Torgo
- LIAAD - Laboratory of Artificial Intelligence and Decision Support, INESC Tec, Porto, Portugal
- Faculty of Computer Science, Dalhousie University, Halifax, Canada, USA
| | - Catarina Magalhães
- CIIMAR/CIMAR - Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Porto, Portugal
- Department of Biology, Faculty of Sciences, University of Porto, Rua Campo Alegre s/n, 4169-007, Porto, Portugal
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16
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Moreira-Coello V, Mouriño-Carballido B, Marañón E, Fernández-Carrera A, Bode A, Sintes E, Zehr JP, Turk-Kubo K, Varela MM. Temporal variability of diazotroph community composition in the upwelling region off NW Iberia. Sci Rep 2019; 9:3737. [PMID: 30842510 PMCID: PMC6403370 DOI: 10.1038/s41598-019-39586-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 01/22/2019] [Indexed: 11/24/2022] Open
Abstract
Knowledge of the ecology of N2-fixing (diazotrophic) plankton is mainly limited to oligotrophic (sub)tropical oceans. However, diazotrophs are widely distributed and active throughout the global ocean. Likewise, relatively little is known about the temporal dynamics of diazotrophs in productive areas. Between February 2014 and December 2015, we carried out 9 one-day samplings in the temperate northwestern Iberian upwelling system to investigate the temporal and vertical variability of the diazotrophic community and its relationship with hydrodynamic forcing. In downwelling conditions, characterized by deeper mixed layers and a homogeneous water column, non-cyanobacterial diazotrophs belonging mainly to nifH clusters 1G (Gammaproteobacteria) and 3 (putative anaerobes) dominated the diazotrophic community. In upwelling and relaxation conditions, affected by enhanced vertical stratification and hydrographic variability, the community was more heterogeneous vertically but less diverse, with prevalence of UCYN-A (unicellular cyanobacteria, subcluster 1B) and non-cyanobacterial diazotrophs from clusters 1G and 3. Oligotyping analysis of UCYN-A phylotype showed that UCYN-A2 sublineage was the most abundant (74%), followed by UCYN-A1 (23%) and UCYN-A4 (2%). UCYN-A1 oligotypes exhibited relatively low frequencies during the three hydrographic conditions, whereas UCYN-A2 showed higher abundances during upwelling and relaxation. Our findings show the presence of a diverse and temporally variable diazotrophic community driven by hydrodynamic forcing in an upwelling system.
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Affiliation(s)
| | | | - Emilio Marañón
- Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Vigo, Spain
| | | | - Antonio Bode
- Instituto Español de Oceanografía, A Coruña, Spain
| | - Eva Sintes
- Instituto Español de Oceanografía, Baleares, Spain
| | - Jonathan P Zehr
- Ocean Sciences Department, University of California, Santa Cruz, California, USA
| | - Kendra Turk-Kubo
- Ocean Sciences Department, University of California, Santa Cruz, California, USA
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17
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Fernández-Gómez B, Díez B, Polz MF, Arroyo JI, Alfaro FD, Marchandon G, Sanhueza C, Farías L, Trefault N, Marquet PA, Molina-Montenegro MA, Sylvander P, Snoeijs-Leijonmalm P. Bacterial community structure in a sympagic habitat expanding with global warming: brackish ice brine at 85-90 °N. THE ISME JOURNAL 2019; 13:316-333. [PMID: 30228379 PMCID: PMC6331608 DOI: 10.1038/s41396-018-0268-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 06/11/2018] [Accepted: 07/24/2018] [Indexed: 01/13/2023]
Abstract
Larger volumes of sea ice have been thawing in the Central Arctic Ocean (CAO) during the last decades than during the past 800,000 years. Brackish brine (fed by meltwater inside the ice) is an expanding sympagic habitat in summer all over the CAO. We report for the first time the structure of bacterial communities in this brine. They are composed of psychrophilic extremophiles, many of them related to phylotypes known from Arctic and Antarctic regions. Community structure displayed strong habitat segregation between brackish ice brine (IB; salinity 2.4-9.6) and immediate sub-ice seawater (SW; salinity 33.3-34.9), expressed at all taxonomic levels (class to genus), by dominant phylotypes as well as by the rare biosphere, and with specialists dominating IB and generalists SW. The dominant phylotypes in IB were related to Candidatus Aquiluna and Flavobacterium, those in SW to Balneatrix and ZD0405, and those shared between the habitats to Halomonas, Polaribacter and Shewanella. A meta-analysis for the oligotrophic CAO showed a pattern with Flavobacteriia dominating in melt ponds, Flavobacteriia and Gammaproteobacteria in solid ice cores, Flavobacteriia, Gamma- and Betaproteobacteria, and Actinobacteria in brine, and Alphaproteobacteria in SW. Based on our results, we expect that the roles of Actinobacteria and Betaproteobacteria in the CAO will increase with global warming owing to the increased production of meltwater in summer. IB contained three times more phylotypes than SW and may act as an insurance reservoir for bacterial diversity that can act as a recruitment base when environmental conditions change.
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Affiliation(s)
- Beatriz Fernández-Gómez
- Department of Molecular Genetics and Microbiology, Pontifical University Catholic of Chile, Santiago, Chile
- INTA-Universidad de Chile, Santiago, Chile
| | - Beatriz Díez
- Department of Molecular Genetics and Microbiology, Pontifical University Catholic of Chile, Santiago, Chile.
- Center for Climate and Resilience Research, Concepción, Chile.
| | - Martin F Polz
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, USA
| | - José Ignacio Arroyo
- Department of Ecology, Pontifical University Catholic of Chile, Santiago, Chile
| | - Fernando D Alfaro
- GEMA Center for Genomics, Ecology & Environment, Universidad Mayor, Santiago, Chile
- Instituto de Ciencias Biológicas, Universidad de Talca, Talca, Chile
| | - Germán Marchandon
- Department of Molecular Genetics and Microbiology, Pontifical University Catholic of Chile, Santiago, Chile
| | - Cynthia Sanhueza
- Department of Molecular Genetics and Microbiology, Pontifical University Catholic of Chile, Santiago, Chile
| | - Laura Farías
- Center for Climate and Resilience Research, Concepción, Chile
- Department of Oceanography, Universidad de Concepción, Concepción, Chile
| | - Nicole Trefault
- GEMA Center for Genomics, Ecology & Environment, Universidad Mayor, Santiago, Chile
| | - Pablo A Marquet
- Department of Ecology, Pontifical University Catholic of Chile, Santiago, Chile
- Instituto de Ecología y Biodiversidad, Universidad de Chile, Santiago, Chile
| | - Marco A Molina-Montenegro
- Instituto de Ciencias Biológicas, Universidad de Talca, Talca, Chile
- Centro de Estudios Avanzados en Zonas Áridas, Universidad Católica del Norte, Coquimbo, Chile
| | - Peter Sylvander
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
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