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Allen-Waller LR, Jones KG, Martynek MP, Brown KT, Barott KL. Comparative physiology reveals heat stress disrupts acid-base homeostasis independent of symbiotic state in the model cnidarian Exaiptasia diaphana. J Exp Biol 2024; 227:jeb246222. [PMID: 38269486 PMCID: PMC10911193 DOI: 10.1242/jeb.246222] [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: 05/31/2023] [Accepted: 01/17/2024] [Indexed: 01/26/2024]
Abstract
Climate change threatens the survival of symbiotic cnidarians by causing photosymbiosis breakdown in a process known as bleaching. Direct effects of temperature on cnidarian host physiology remain difficult to describe because heatwaves depress symbiont performance, leading to host stress and starvation. The symbiotic sea anemone Exaiptasia diaphana provides an opportune system to disentangle direct versus indirect heat effects on the host, as it can survive indefinitely without symbionts. We tested the hypothesis that heat directly impairs cnidarian physiology by comparing symbiotic and aposymbiotic individuals of two laboratory subpopulations of a commonly used clonal strain of E. diaphana, CC7. We exposed anemones to a range of temperatures (ambient, +2°C, +4°C and +6°C) for 15-18 days, then measured their symbiont population densities, autotrophic carbon assimilation and translocation, photosynthesis, respiration and host intracellular pH (pHi). Symbiotic anemones from the two subpopulations differed in size and symbiont density and exhibited distinct heat stress responses, highlighting the importance of acclimation to different laboratory conditions. Specifically, the cohort with higher initial symbiont densities experienced dose-dependent symbiont loss with increasing temperature and a corresponding decline in host photosynthate accumulation. In contrast, the cohort with lower initial symbiont densities did not lose symbionts or assimilate less photosynthate when heated, similar to the response of aposymbiotic anemones. However, anemone pHi decreased at higher temperatures regardless of cohort, symbiont presence or photosynthate translocation, indicating that heat consistently disrupts cnidarian acid-base homeostasis independent of symbiotic status or mutualism breakdown. Thus, pH regulation may be a critical vulnerability for cnidarians in a changing climate.
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Affiliation(s)
| | - Katelyn G. Jones
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Kristen T. Brown
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Katie L. Barott
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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2
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Calcification in Three Common Calcified Algae from Phuket, Thailand: Potential Relevance on Seawater Carbonate Chemistry and Link to Photosynthetic Process. PLANTS 2021; 10:plants10112537. [PMID: 34834900 PMCID: PMC8624766 DOI: 10.3390/plants10112537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/11/2021] [Accepted: 11/19/2021] [Indexed: 11/25/2022]
Abstract
Calcifying macroalgae contribute significantly to the structure and function of tropical marine ecosystems. Their calcification and photosynthetic processes are not well understood despite their critical role in marine carbon cycles and high vulnerability to environmental changes. This study aims to provide a better understanding of the macroalgal calcification process, focusing on its relevance concerning seawater carbonate chemistry and its relationship to photosynthesis in three dominant calcified macroalgae in Thailand, Padina boryana, Halimeda macroloba and Halimeda opuntia. Morphological and microstructural attributes of the three macroalgae were analyzed and subsequently linked to their calcification rates and responses to inhibition of photosynthesis. In the first experiment, seawater pH, total alkalinity and total dissolved inorganic carbon were measured after incubation of the macroalgae in the light and after equilibration of the seawater with air. Estimations of carbon uptake into photosynthesis and calcification and carbon release into air were obtained thereafter. Our results provide evidence that calcification of the three calcified macroalgae is a potential source of CO2, where calcification by H. opuntia and H. macroloba leads to a greater release of CO2 per biomass weight than P. boryana. Nevertheless, this capacity is expected to vary on a diurnal basis, as the second experiment indicates that calcification is highly coupled to photosynthetic activity. Lower pH as a result of inhibited photosynthesis under darkness imposes more negative effects on H. opuntia and H. macroloba than on P. boryana, implying that they are more sensitive to acidification. These effects were worsened when photosynthesis was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, highlighting the significance of photosynthetic electron transport-dependent processes. Our findings suggest that estimations of the amount of carbon stored in the vegetated marine ecosystems should account for macroalgal calcification as a potential carbon source while considering diurnal variations in photosynthesis and seawater pH in a natural setting.
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3
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Capasso L, Ganot P, Planas-Bielsa V, Tambutté S, Zoccola D. Intracellular pH regulation: characterization and functional investigation of H + transporters in Stylophora pistillata. BMC Mol Cell Biol 2021; 22:18. [PMID: 33685406 PMCID: PMC7941709 DOI: 10.1186/s12860-021-00353-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/22/2021] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Reef-building corals regularly experience changes in intra- and extracellular H+ concentrations ([H+]) due to physiological and environmental processes. Stringent control of [H+] is required to maintain the homeostatic acid-base balance in coral cells and is achieved through the regulation of intracellular pH (pHi). This task is especially challenging for reef-building corals that share an endosymbiotic relationship with photosynthetic dinoflagellates (family Symbiodinaceae), which significantly affect the pHi of coral cells. Despite their importance, the pH regulatory proteins involved in the homeostatic acid-base balance have been scarcely investigated in corals. Here, we report in the coral Stylophora pistillata a full characterization of the genomic structure, domain topology and phylogeny of three major H+ transporter families that are known to play a role in the intracellular pH regulation of animal cells; we investigated their tissue-specific expression patterns and assessed the effect of seawater acidification on their expression levels. RESULTS We identified members of the Na+/H+ exchanger (SLC9), vacuolar-type electrogenic H+-ATP hydrolase (V-ATPase) and voltage-gated proton channel (HvCN) families in the genome and transcriptome of S. pistillata. In addition, we identified a novel member of the HvCN gene family in the cnidarian subclass Hexacorallia that has not been previously described in any species. We also identified key residues that contribute to H+ transporter substrate specificity, protein function and regulation. Last, we demonstrated that some of these proteins have different tissue expression patterns, and most are unaffected by exposure to seawater acidification. CONCLUSIONS In this study, we provide the first characterization of H+ transporters that might contribute to the homeostatic acid-base balance in coral cells. This work will enrich the knowledge of the basic aspects of coral biology and has important implications for our understanding of how corals regulate their intracellular environment.
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Affiliation(s)
- Laura Capasso
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco.,Sorbonne Université, Collège Doctoral, F-75005, Paris, France
| | - Philippe Ganot
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco
| | | | - Sylvie Tambutté
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco
| | - Didier Zoccola
- Centre Scientifique de Monaco, 8 quai Antoine 1er, 98000, Monaco, Monaco.
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4
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Yoshioka Y, Yamashita H, Suzuki G, Zayasu Y, Tada I, Kanda M, Satoh N, Shoguchi E, Shinzato C. Whole-Genome Transcriptome Analyses of Native Symbionts Reveal Host Coral Genomic Novelties for Establishing Coral-Algae Symbioses. Genome Biol Evol 2020; 13:5981117. [PMID: 33185681 PMCID: PMC7850063 DOI: 10.1093/gbe/evaa240] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2020] [Indexed: 01/14/2023] Open
Abstract
Reef-building corals and photosynthetic, endosymbiotic algae of the family Symbiodiniaceae establish mutualistic relationships that are fundamental to coral biology, enabling coral reefs to support a vast diversity of marine species. Although numerous types of Symbiodiniaceae occur in coral reef environments, Acropora corals select specific types in early life stages. In order to study molecular mechanisms of coral–algal symbioses occurring in nature, we performed whole-genome transcriptomic analyses of Acropora tenuis larvae inoculated with Symbiodinium microadriaticum strains isolated from an Acropora recruit. In order to identify genes specifically involved in symbioses with native symbionts in early life stages, we also investigated transcriptomic responses of Acropora larvae exposed to closely related, nonsymbiotic, and occasionally symbiotic Symbiodinium strains. We found that the number of differentially expressed genes was largest when larvae acquired native symbionts. Repertoires of differentially expressed genes indicated that corals reduced amino acid, sugar, and lipid metabolism, such that metabolic enzymes performing these functions were derived primarily from S. microadriaticum rather than from A. tenuis. Upregulated gene expression of transporters for those metabolites occurred only when coral larvae acquired their natural symbionts, suggesting active utilization of native symbionts by host corals. We also discovered that in Acropora, genes for sugar and amino acid transporters, prosaposin-like, and Notch ligand-like, were upregulated only in response to native symbionts, and included tandemly duplicated genes. Gene duplications in coral genomes may have been essential to establish genomic novelties for coral–algae symbiosis.
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Affiliation(s)
- Yuki Yoshioka
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan.,Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Hiroshi Yamashita
- Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Ishigaki, Okinawa, Japan
| | - Go Suzuki
- Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Ishigaki, Okinawa, Japan
| | - Yuna Zayasu
- Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan
| | - Ipputa Tada
- Department of Genetics, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka, Japan
| | - Miyuki Kanda
- DNA Sequencing Section (SQC), Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan
| | - Noriyuki Satoh
- Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan
| | - Eiichi Shoguchi
- Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan
| | - Chuya Shinzato
- Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
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5
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van Oppen MJH, Medina M. Coral evolutionary responses to microbial symbioses. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190591. [PMID: 32772672 PMCID: PMC7435167 DOI: 10.1098/rstb.2019.0591] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2020] [Indexed: 12/19/2022] Open
Abstract
This review explores how microbial symbioses may have influenced and continue to influence the evolution of reef-building corals (Cnidaria; Scleractinia). The coral holobiont comprises a diverse microbiome including dinoflagellate algae (Dinophyceae; Symbiodiniaceae), bacteria, archaea, fungi and viruses, but here we focus on the Symbiodiniaceae as knowledge of the impact of other microbial symbionts on coral evolution is scant. Symbiosis with Symbiodiniaceae has extended the coral's metabolic capacity through metabolic handoffs and horizontal gene transfer (HGT) and has contributed to the ecological success of these iconic organisms. It necessitated the prior existence or the evolution of a series of adaptations of the host to attract and select the right symbionts, to provide them with a suitable environment and to remove disfunctional symbionts. Signatures of microbial symbiosis in the coral genome include HGT from Symbiodiniaceae and bacteria, gene family expansions, and a broad repertoire of oxidative stress response and innate immunity genes. Symbiosis with Symbiodiniaceae has permitted corals to occupy oligotrophic waters as the algae provide most corals with the majority of their nutrition. However, the coral-Symbiodiniaceae symbiosis is sensitive to climate warming, which disrupts this intimate relationship, causing coral bleaching, mortality and a worldwide decline of coral reefs. This article is part of the theme issue 'The role of the microbiome in host evolution'.
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Affiliation(s)
- Madeleine J. H. van Oppen
- School of BioSciences, The University of Melbourne, Parkville, 3010 Victoria, Australia
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, 4810 Queensland, Australia
| | - Mónica Medina
- Department of Biology, The Pennsylvania State University, 208 Mueller Lab, University Park, PA 16802, USA
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6
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Tresguerres M, Clifford AM, Harter TS, Roa JN, Thies AB, Yee DP, Brauner CJ. Evolutionary links between intra- and extracellular acid-base regulation in fish and other aquatic animals. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:449-465. [PMID: 32458594 DOI: 10.1002/jez.2367] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/10/2020] [Accepted: 05/06/2020] [Indexed: 12/17/2022]
Abstract
The acid-base relevant molecules carbon dioxide (CO2 ), protons (H+ ), and bicarbonate (HCO3 - ) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid-base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO2 , H+ , and HCO3 - have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways. Life in aquatic environments presents organisms with distinct acid-base challenges that are not found in terrestrial environments. These include a relatively high CO2 relative to O2 solubility that prevents internal CO2 /HCO3 - accumulation to buffer pH, a lower O2 content that may favor anaerobic metabolism, and variable environmental CO2 , pH and O2 levels that require dynamic adjustments in acid-base homeostatic mechanisms. Additionally, some aquatic animals purposely create acidic or alkaline microenvironments that drive specialized physiological functions. For example, acidifying mechanisms can enhance O2 delivery by red blood cells, lead to ammonia trapping for excretion or buoyancy purposes, or lead to CO2 accumulation to promote photosynthesis by endosymbiotic algae. On the other hand, alkalinizing mechanisms can serve to promote calcium carbonate skeletal formation. This nonexhaustive review summarizes some of the distinct acid-base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Alexander M Clifford
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Angus B Thies
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Daniel P Yee
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, Canada
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7
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Effects of light and darkness on pH regulation in three coral species exposed to seawater acidification. Sci Rep 2019; 9:2201. [PMID: 30778093 PMCID: PMC6379376 DOI: 10.1038/s41598-018-38168-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 12/20/2018] [Indexed: 02/07/2023] Open
Abstract
The resilience of corals to ocean acidification has been proposed to rely on regulation of extracellular calcifying medium pH (pHECM), but few studies have compared the capacity of coral species to control this parameter at elevated pCO2. Furthermore, exposure to light and darkness influences both pH regulation and calcification in corals, but little is known about its effect under conditions of seawater acidification. Here we investigated the effect of acidification in light and darkness on pHECM, calcifying cell intracellular pH (pHI), calcification, photosynthesis and respiration in three coral species: Stylophora pistillata, Pocillopora damicornis and Acropora hyacinthus. We show that S. pistillata was able to maintain pHECM under acidification in light and darkness, but pHECM decreased in P. damicornis and A. hyacinthus to a much greater extent in darkness than in the light. Acidification depressed calcifying cell pHI in all three species, but we identified an unexpected positive effect of light on pHI. Calcification rate and pHECM decreased together under acidification, but there are inconsistencies in their relationship indicating that other physiological parameters are likely to shape how coral calcification responds to acidification. Overall our study reveals interspecies differences in coral regulation of pHECM and pHI when exposed to acidification, influenced by exposure to light and darkness.
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8
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Putnam HM, Barott KL, Ainsworth TD, Gates RD. The Vulnerability and Resilience of Reef-Building Corals. Curr Biol 2018; 27:R528-R540. [PMID: 28586690 DOI: 10.1016/j.cub.2017.04.047] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Reef-building corals provide the foundation for the structural and biological diversity of coral-reef ecosystems. These massive biological structures, which can be seen from space, are the culmination of complex interactions between the tiny polyps of the coral animal in concert with its unicellular symbiotic algae and a wide diversity of closely associated microorganisms (bacteria, archaea, fungi, and viruses). While reef-building corals have persisted in various forms for over 200 million years, human-induced conditions threaten their function and persistence. The scope for loss associated with the destruction of coral reef systems is economically, biologically, physically and culturally immense. Here, we provide a micro-to-macro perspective on the biology of scleractinian corals and discuss how cellular processes of the host and symbionts potentially affect the response of these reef builders to the wide variety of both natural and anthropogenic stressors encountered by corals in the Anthropocene. We argue that the internal physicochemical settings matter to both the performance of the host and microbiome, as bio-physical feedbacks may enhance stress tolerance through environmentally mediated host priming and effects on microbiome ecological and evolutionary dynamics.
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Affiliation(s)
- Hollie M Putnam
- University of Rhode Island, Department of Biological Sciences, Kingston, RI, USA.
| | - Katie L Barott
- University of Pennsylvania, Department of Biology, Philadelphia, PA, USA; Hawaii Institute for Marine Biology, University of Hawai'i, Manoa, HI, USA
| | - Tracy D Ainsworth
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Australia
| | - Ruth D Gates
- Hawaii Institute for Marine Biology, University of Hawai'i, Manoa, HI, USA
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9
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Barott KL, Barron ME, Tresguerres M. Identification of a molecular pH sensor in coral. Proc Biol Sci 2018; 284:rspb.2017.1769. [PMID: 29093223 DOI: 10.1098/rspb.2017.1769] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/04/2017] [Indexed: 12/26/2022] Open
Abstract
Maintaining stable intracellular pH (pHi) is essential for homeostasis, and requires the ability to both sense pH changes that may result from internal and external sources, and to regulate downstream compensatory pH pathways. Here we identified the cAMP-producing enzyme soluble adenylyl cyclase (sAC) as the first molecular pH sensor in corals. sAC protein was detected throughout coral tissues, including those involved in symbiosis and calcification. Application of a sAC-specific inhibitor caused significant and reversible pHi acidosis in isolated coral cells under both dark and light conditions, indicating sAC is essential for sensing and regulating pHi perturbations caused by respiration and photosynthesis. Furthermore, pHi regulation during external acidification was also dependent on sAC activity. Thus, sAC is a sensor and regulator of pH disturbances from both metabolic and external origin in corals. Since sAC is present in all coral cell types, and the cAMP pathway can regulate virtually every aspect of cell physiology through post-translational modifications of proteins, sAC is likely to trigger multiple homeostatic mechanisms in response to pH disturbances. This is also the first evidence that sAC modulates pHi in any non-mammalian animal. Since corals are basal metazoans, our results indicate this function is evolutionarily conserved across animals.
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Affiliation(s)
- Katie L Barott
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.,Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Megan E Barron
- Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Martin Tresguerres
- Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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10
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How does an animal behave like a plant? Physiological and molecular adaptations of zooxanthellae and their hosts to symbiosis. C R Biol 2018; 341:276-280. [DOI: 10.1016/j.crvi.2018.03.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 03/13/2018] [Indexed: 12/26/2022]
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11
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Duhamel S, Van Wambeke F, Lefevre D, Benavides M, Bonnet S. Mixotrophic metabolism by natural communities of unicellular cyanobacteria in the western tropical South Pacific Ocean. Environ Microbiol 2018; 20:2743-2756. [PMID: 29573372 DOI: 10.1111/1462-2920.14111] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 03/12/2018] [Accepted: 03/17/2018] [Indexed: 12/31/2022]
Abstract
Cyanobacteria are major contributors to ocean biogeochemical cycling. However, mixotrophic metabolism and the relative importance of inorganic and organic carbon assimilation within the most abundant cyanobacteria are still poorly understood. We explore the ability of Prochlorococcus and Synechococcus to assimilate organic molecules with variable C:N:P composition and its modulation by light availability and photosynthetic impairment. We used a combination of radiolabelled molecules incubations with flow cytometry cell sorting to separate picoplankton groups from the western tropical South Pacific Ocean. Prochlorococcus and Synechococcus assimilated glucose, leucine and ATP at all stations, but cell-specific assimilation rates of N and P containing molecules were significantly higher than glucose. Incubations in the dark or with an inhibitor of photosystem II resulted in reduced assimilation rates. Light-enhanced cell-specific glucose uptake was generally higher for cyanobacteria (∼50%) than for the low nucleic acid fraction of bacterioplankton (LNA, ∼35%). Our results confirm previous findings, based mainly on cultures and genomic potentials, showing that Prochlorococcus and Synechococcus have a flexible mixotrophic metabolism, but demonstrate that natural populations remain primarily photoautotrophs. Our findings indicate that mixotrophy by marine cyanobacteria is more likely to be an adaptation to low inorganic nutrient availability rather than a facultative pathway for carbon acquisition.
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Affiliation(s)
- Solange Duhamel
- Lamont Doherty Earth Observatory, Division of Biology and Paleo Environment, PO Box 1000, 61 Route 9W, Palisades, NY 10964, USA
| | - France Van Wambeke
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Dominique Lefevre
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
| | - Mar Benavides
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.,Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 98848, Noumea, New Caledonia
| | - Sophie Bonnet
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.,Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 98848, Noumea, New Caledonia
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12
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Le Goff C, Tambutté E, Venn AA, Techer N, Allemand D, Tambutté S. In vivo pH measurement at the site of calcification in an octocoral. Sci Rep 2017; 7:11210. [PMID: 28894174 PMCID: PMC5593875 DOI: 10.1038/s41598-017-10348-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 08/03/2017] [Indexed: 11/21/2022] Open
Abstract
Calcareous octocorals are ecologically important calcifiers, but little is known about their biomineralization physiology, relative to scleractinian corals. Many marine calcifiers promote calcification by up-regulating pH at calcification sites against the surrounding seawater. Here, we investigated pH in the red octocoral Corallium rubrum which forms sclerites and an axial skeleton. To achieve this, we cultured microcolonies on coverslips facilitating microscopy of calcification sites of sclerites and axial skeleton. Initially we conducted extensive characterisation of the structural arrangement of biominerals and calcifying cells in context with other tissues, and then measured pH by live tissue imaging. Our results reveal that developing sclerites are enveloped by two scleroblasts and an extracellular calcifying medium of pH 7.97 ± 0.15. Similarly, axial skeleton crystals are surrounded by cells and a calcifying medium of pH 7.89 ± 0.09. In both cases, calcifying media are more alkaline compared to calcifying cells and fluids in gastrovascular canals, but importantly they are not pH up-regulated with respect to the surrounding seawater, contrary to what is observed in scleractinians. This points to a potential vulnerability of this species to decrease in seawater pH and is consistent with reports that red coral calcification is sensitive to ocean acidification.
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Affiliation(s)
- C Le Goff
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco
| | - E Tambutté
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco
| | - A A Venn
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco
| | - N Techer
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco
| | - D Allemand
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco
| | - S Tambutté
- Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine Ier, MC-98000, Monaco, Monaco.
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13
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Klein SG, Pitt KA, Nitschke MR, Goyen S, Welsh DT, Suggett DJ, Carroll AR. Symbiodinium mitigate the combined effects of hypoxia and acidification on a noncalcifying cnidarian. GLOBAL CHANGE BIOLOGY 2017; 23:3690-3703. [PMID: 28390081 DOI: 10.1111/gcb.13718] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 03/28/2017] [Accepted: 04/02/2017] [Indexed: 05/23/2023]
Abstract
Anthropogenic nutrient inputs enhance microbial respiration within many coastal ecosystems, driving concurrent hypoxia and acidification. During photosynthesis, Symbiodinium spp., the microalgal endosymbionts of cnidarians and other marine phyla, produce O2 and assimilate CO2 and thus potentially mitigate the exposure of the host to these stresses. However, such a role for Symbiodinium remains untested for noncalcifying cnidarians. We therefore contrasted the fitness of symbiotic and aposymbiotic polyps of a model host jellyfish (Cassiopea sp.) under reduced O2 (~2.09 mg/L) and pH (~ 7.63) scenarios in a full-factorial experiment. Host fitness was characterized as asexual reproduction and their ability to regulate internal pH and Symbiodinium performance characterized by maximum photochemical efficiency, chla content and cell density. Acidification alone resulted in 58% more asexual reproduction of symbiotic polyps than aposymbiotic polyps (and enhanced Symbiodinium cell density) suggesting Cassiopea sp. fitness was enhanced by CO2 -stimulated Symbiodinium photosynthetic activity. Indeed, greater CO2 drawdown (elevated pH) was observed within host tissues of symbiotic polyps under acidification regardless of O2 conditions. Hypoxia alone produced 22% fewer polyps than ambient conditions regardless of acidification and symbiont status, suggesting Symbiodinium photosynthetic activity did not mitigate its effects. Combined hypoxia and acidification, however, produced similar numbers of symbiotic polyps compared with aposymbiotic kept under ambient conditions, demonstrating that the presence of Symbiodinium was key for mitigating the combined effects of hypoxia and acidification on asexual reproduction. We hypothesize that this mitigation occurred because of reduced photorespiration under elevated CO2 conditions where increased net O2 production ameliorates oxygen debt. We show that Symbiodinium play an important role in facilitating enhanced fitness of Cassiopea sp. polyps, and perhaps also other noncalcifying cnidarian hosts, to the ubiquitous effects of ocean acidification. Importantly we highlight that symbiotic, noncalcifying cnidarians may be particularly advantaged in productive coastal waters that are subject to simultaneous hypoxia and acidification.
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Affiliation(s)
- Shannon G Klein
- Australian Rivers Institute - Coasts and Estuaries, Griffith School of Environment, Griffith University, Gold Coast, Qld, Australia
- Red Sea Research Center (RSRC), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Kylie A Pitt
- Australian Rivers Institute - Coasts and Estuaries, Griffith School of Environment, Griffith University, Gold Coast, Qld, Australia
| | - Matthew R Nitschke
- Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, Australia
| | - Samantha Goyen
- Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, Australia
| | - David T Welsh
- Environmental Futures Research Institute, Griffith School of Environment, Griffith University, Gold Coast, Qld, Australia
| | - David J Suggett
- Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, Australia
| | - Anthony R Carroll
- Environmental Futures Research Institute, Griffith School of Environment, Griffith University, Gold Coast, Qld, Australia
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14
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Marcelino VR, Morrow KM, Oppen MJH, Bourne DG, Verbruggen H. Diversity and stability of coral endolithic microbial communities at a naturally high
p
CO
2
reef. Mol Ecol 2017; 26:5344-5357. [DOI: 10.1111/mec.14268] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 06/29/2017] [Accepted: 06/30/2017] [Indexed: 12/15/2022]
Affiliation(s)
| | - Kathleen M. Morrow
- Department of Molecular, Cellular and Biomedical Sciences University of New Hampshire Durham NH USA
- Australian Institute of Marine Science Townsville Qld Australia
| | - Madeleine J. H. Oppen
- School of Biosciences University of Melbourne Melbourne Vic. Australia
- Australian Institute of Marine Science Townsville Qld Australia
| | - David G. Bourne
- Australian Institute of Marine Science Townsville Qld Australia
- College of Science and Engineering James Cook University Townville Qld Australia
| | - Heroen Verbruggen
- School of Biosciences University of Melbourne Melbourne Vic. Australia
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15
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Weston AJ, Dunlap WC, Beltran VH, Starcevic A, Hranueli D, Ward M, Long PF. Proteomics links the redox state to calcium signaling during bleaching of the scleractinian coral Acropora microphthalma on exposure to high solar irradiance and thermal stress. Mol Cell Proteomics 2015; 14:585-95. [PMID: 25561505 PMCID: PMC4349979 DOI: 10.1074/mcp.m114.043125] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 08/08/2014] [Indexed: 11/06/2022] Open
Abstract
Shipboard experiments were each performed over a 2 day period to examine the proteomic response of the symbiotic coral Acropora microphthalma exposed to acute conditions of high temperature/low light or high light/low temperature stress. During these treatments, corals had noticeably bleached. The photosynthetic performance of residual algal endosymbionts was severely impaired but showed signs of recovery in both treatments by the end of the second day. Changes in the coral proteome were determined daily and, using recently available annotated genome sequences, the individual contributions of the coral host and algal endosymbionts could be extracted from these data. Quantitative changes in proteins relevant to redox state and calcium metabolism are presented. Notably, expression of common antioxidant proteins was not detected from the coral host but present in the algal endosymbiont proteome. Possible roles for elevated carbonic anhydrase in the coral host are considered: to restore intracellular pH diminished by loss of photosynthetic activity, to indirectly limit intracellular calcium influx linked with enhanced calmodulin expression to impede late-stage symbiont exocytosis, or to enhance inorganic carbon transport to improve the photosynthetic performance of algal symbionts that remain in hospite. Protein effectors of calcium-dependent exocytosis were present in both symbiotic partners. No caspase-family proteins associated with host cell apoptosis, with exception of the autophagy chaperone HSP70, were detected, suggesting that algal loss and photosynthetic dysfunction under these experimental conditions were not due to host-mediated phytosymbiont destruction. Instead, bleaching occurred by symbiont exocytosis and loss of light-harvesting pigments of algae that remain in hospite. These proteomic data are, therefore, consistent with our premise that coral endosymbionts can mediate their own retention or departure from the coral host, which may manifest as "symbiont shuffling" of Symbiodinium clades in response to environmental stress.
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Affiliation(s)
- Andrew J Weston
- From the ‡King's College London Proteomics Facility, Institute of Psychiatry, London SE5 8AF, UK
| | - Walter C Dunlap
- §Centre for Marine Microbiology and Genetics, Australian Institute of Marine Science, PMB No. 3 Townsville MC, Townsville, Queensland,4810 Australia. ‖Institute of Pharmaceutical Science, Kings College, Strand, London WC2R 2LS, United Kingdom
| | - Victor H Beltran
- §Centre for Marine Microbiology and Genetics, Australian Institute of Marine Science, PMB No. 3 Townsville MC, Townsville, Queensland,4810 Australia. ¶ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville QLD 4811 Australia
| | - Antonio Starcevic
- ‡‡Section for Bioinformatics, Department of Biochemical Engineering, Faculty of Food Technology & Biotechnology, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
| | - Daslav Hranueli
- ‡‡Section for Bioinformatics, Department of Biochemical Engineering, Faculty of Food Technology & Biotechnology, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
| | - Malcolm Ward
- From the ‡King's College London Proteomics Facility, Institute of Psychiatry, London SE5 8AF, UK
| | - Paul F Long
- ‖Institute of Pharmaceutical Science, Kings College, Strand, London WC2R 2LS, United Kingdom, **Department of Chemistry, King's College Strand, London WC2R 2LS, United Kingdom, Franklin-Wilkins Building, Stamford Street, London SE1 9NH, UK
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16
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Barott KL, Venn AA, Perez SO, Tambutté S, Tresguerres M. Coral host cells acidify symbiotic algal microenvironment to promote photosynthesis. Proc Natl Acad Sci U S A 2015; 112:607-12. [PMID: 25548188 PMCID: PMC4299235 DOI: 10.1073/pnas.1413483112] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Symbiotic dinoflagellate algae residing inside coral tissues supply the host with the majority of their energy requirements through the translocation of photosynthetically fixed carbon. The algae, in turn, rely on the host for the supply of inorganic carbon. Carbon must be concentrated as CO2 in order for photosynthesis to proceed, and here we show that the coral host plays an active role in this process. The host-derived symbiosome membrane surrounding the algae abundantly expresses vacuolar H(+)-ATPase (VHA), which acidifies the symbiosome space down to pH ∼ 4. Inhibition of VHA results in a significant decrease in average H(+) activity in the symbiosome of up to 75% and a significant reduction in O2 production rate, a measure of photosynthetic activity. These results suggest that host VHA is part of a previously unidentified carbon concentrating mechanism for algal photosynthesis and provide mechanistic evidence that coral host cells can actively modulate the physiology of their symbionts.
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Affiliation(s)
- Katie L Barott
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093
| | - Alexander A Venn
- Marine Biology Department, Centre Scientifique de Monaco, MC-98000 Monaco, Monaco; and Laboratoire Européen Associé 647 "Biosensib," Centre Scientifique de Monaco-Centre National de la Recherche Scientifique, MC-98000 Monaco, Monaco
| | - Sidney O Perez
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093
| | - Sylvie Tambutté
- Marine Biology Department, Centre Scientifique de Monaco, MC-98000 Monaco, Monaco; and
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093;
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17
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Roth MS. The engine of the reef: photobiology of the coral-algal symbiosis. Front Microbiol 2014; 5:422. [PMID: 25202301 PMCID: PMC4141621 DOI: 10.3389/fmicb.2014.00422] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 07/25/2014] [Indexed: 01/09/2023] Open
Abstract
Coral reef ecosystems thrive in tropical oligotrophic oceans because of the relationship between corals and endosymbiotic dinoflagellate algae called Symbiodinium. Symbiodinium convert sunlight and carbon dioxide into organic carbon and oxygen to fuel coral growth and calcification, creating habitat for these diverse and productive ecosystems. Light is thus a key regulating factor shaping the productivity, physiology, and ecology of the coral holobiont. Similar to all oxygenic photoautotrophs, Symbiodinium must safely harvest sunlight for photosynthesis and dissipate excess energy to prevent oxidative stress. Oxidative stress is caused by environmental stressors such as those associated with global climate change, and ultimately leads to breakdown of the coral-algal symbiosis known as coral bleaching. Recently, large-scale coral bleaching events have become pervasive and frequent threatening and endangering coral reefs. Because the coral-algal symbiosis is the biological engine producing the reef, the future of coral reef ecosystems depends on the ecophysiology of the symbiosis. This review examines the photobiology of the coral-algal symbiosis with particular focus on the photophysiological responses and timescales of corals and Symbiodinium. Additionally, this review summarizes the light environment and its dynamics, the vulnerability of the symbiosis to oxidative stress, the abiotic and biotic factors influencing photosynthesis, the diversity of the coral-algal symbiosis, and recent advances in the field. Studies integrating physiology with the developing "omics" fields will provide new insights into the coral-algal symbiosis. Greater physiological and ecological understanding of the coral-algal symbiosis is needed for protection and conservation of coral reefs.
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Affiliation(s)
- Melissa S. Roth
- Department of Plant and Microbial Biology, University of California BerkeleyBerkeley, CA, USA
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18
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Gibbin EM, Putnam HM, Davy SK, Gates RD. Intracellular pH and its response to CO2-driven seawater acidification in symbiotic versus non-symbiotic coral cells. J Exp Biol 2014; 217:1963-9. [DOI: 10.1242/jeb.099549] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Regulating intracellular pH (pHi) is critical for optimising the metabolic activity of corals, yet mechanisms involved in pH regulation and the buffering capacity within coral cells are not well understood. Our study investigated how the presence of symbiotic dinoflagellates affects the response of pHi to pCO2-driven seawater acidification in cells isolated from Pocillopora damicornis. Using the fluorescent dye BCECF-AM, in conjunction with confocal microscopy, we simultaneously characterised the response of pHi in host coral cells and their dinoflagellate symbionts, in symbiotic and non-symbiotic states under saturating light, with and without the photosynthetic inhibitor DCMU. Each treatment was run under control (pH 7.8) and CO2 acidified seawater conditions (decreasing pH from 7.8 - 6.8). After two hours of CO2 addition, by which time the external pH (pHe) had declined to 6.8, the dinoflagellate symbionts had increased their pHi by 0.5 pH units above control levels. In contrast, in both symbiotic and non-symbiotic host coral cells, 15 min of CO2 addition (0.2 pH unit drop in pHe) led to cytoplasmic acidosis equivalent to 0.4 pH units. Despite further seawater acidification over the duration of the experiment, the pHi of non-symbiotic coral cells did not change, though in host cells containing a symbiont cell the pHi recovered to control levels. This recovery was negated when cells were incubated with DCMU. Our results reveal that photosynthetic activity of the endosymbiont is tightly coupled with the ability of the host cell to recover from cellular acidosis after exposure to high CO2 / low pH.
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19
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Laurent J, Venn A, Tambutté É, Ganot P, Allemand D, Tambutté S. Regulation of intracellular pH in cnidarians: response to acidosis in Anemonia viridis. FEBS J 2013; 281:683-95. [PMID: 24256552 DOI: 10.1111/febs.12614] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/07/2013] [Accepted: 11/11/2013] [Indexed: 11/28/2022]
Abstract
The regulation of intracellular pH (pHi) is a fundamental aspect of cell physiology that has received little attention in studies of the phylum Cnidaria, which includes ecologically important sea anemones and reef-building corals. Like all organisms, cnidarians must maintain pH homeostasis to counterbalance reductions in pHi, which can arise because of changes in either intrinsic or extrinsic parameters. Corals and sea anemones face natural daily changes in internal fluids, where the extracellular pH can range from 8.9 during the day to 7.4 at night. Furthermore, cnidarians are likely to experience future CO₂-driven declines in seawater pH, a process known as ocean acidification. Here, we carried out the first mechanistic investigation to determine how cnidarian pHi regulation responds to decreases in extracellular and intracellular pH. Using the anemone Anemonia viridis, we employed confocal live cell imaging and a pH-sensitive dye to track the dynamics of pHi after intracellular acidosis induced by acute exposure to decreases in seawater pH and NH₄Cl prepulses. The investigation was conducted on cells that contained intracellular symbiotic algae (Symbiodinium sp.) and on symbiont-free endoderm cells. Experiments using inhibitors and Na⁺-free seawater indicate a potential role of Na⁺/H⁺ plasma membrane exchangers (NHEs) in mediating pHi recovery following intracellular acidosis in both cell types. We also measured the buffering capacity of cells, and obtained values between 20.8 and 43.8 mM per pH unit, which are comparable to those in other invertebrates. Our findings provide the first steps towards a better understanding of acid-base regulation in these basal metazoans, for which information on cell physiology is extremely limited.
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20
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Barott KL, Helman Y, Haramaty L, Barron ME, Hess KC, Buck J, Levin LR, Tresguerres M. High adenylyl cyclase activity and in vivo cAMP fluctuations in corals suggest central physiological role. Sci Rep 2013; 3:1379. [PMID: 23459251 PMCID: PMC3587883 DOI: 10.1038/srep01379] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 02/20/2013] [Indexed: 11/29/2022] Open
Abstract
Corals are an ecologically and evolutionarily significant group, providing the framework for coral reef biodiversity while representing one of the most basal of metazoan phyla. However, little is known about fundamental signaling pathways in corals. Here we investigate the dynamics of cAMP, a conserved signaling molecule that can regulate virtually every physiological process. Bioinformatics revealed corals have both transmembrane and soluble adenylyl cyclases (AC). Endogenous cAMP levels in live corals followed a potential diel cycle, as they were higher during the day compared to the middle of the night. Coral homogenates exhibited some of the highest cAMP production rates ever to be recorded in any organism; this activity was inhibited by calcium ions and stimulated by bicarbonate. In contrast, zooxanthellae or mucus had >1000-fold lower AC activity. These results suggest that cAMP is an important regulator of coral physiology, especially in response to light, acid/base disturbances and inorganic carbon levels.
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Affiliation(s)
- K. L. Barott
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
| | - Y. Helman
- Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, New Jersey, United States of America
- Current address: Department of Plant Pathology and Microbiology, Hebrew University of Jerusalem, Israel
| | - L. Haramaty
- Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, New Jersey, United States of America
| | - M. E. Barron
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
| | - K. C. Hess
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - J. Buck
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - L. R. Levin
- Weill Cornell Medical College, Department of Pharmacology, New York City, New York, United States of America
| | - M. Tresguerres
- Scripps Institution of Oceanography, Marine Biology Research Division, La Jolla, California, United States of America
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