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Intriguing Diversity Among Diazotrophic Picoplankton Along a Mediterranean Transect: from the Origin of Plastids to the Dominance of Rhizobia : Volume 7, Issue 6 (02/12/2010)

By Le Moal, M.

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Book Id: WPLBN0004005656
Format Type: PDF Article :
File Size: Pages 38
Reproduction Date: 2015

Title: Intriguing Diversity Among Diazotrophic Picoplankton Along a Mediterranean Transect: from the Origin of Plastids to the Dominance of Rhizobia : Volume 7, Issue 6 (02/12/2010)  
Author: Le Moal, M.
Volume: Vol. 7, Issue 6
Language: English
Subject: Science, Biogeosciences, Discussions
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2010
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Biegala, I. C., Collin, H., & Moal, M. L. (2010). Intriguing Diversity Among Diazotrophic Picoplankton Along a Mediterranean Transect: from the Origin of Plastids to the Dominance of Rhizobia : Volume 7, Issue 6 (02/12/2010). Retrieved from http://www.ebooklibrary.org/


Description
Description: CNRS-INSU/IRD/Université de la Méditerranée, UMR 6535, Laboratoire d'Océanographie Physique et Biogéochimique, Centre d'Océanologie de Marseille, 11 rue Batterie des Lions, 13007 Marseille, France. The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has been formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH phylogenies. These genetic analyses were possible owning to the development of a new PCR protocol adapted for scarce microorganisms (0.2 cell ml−1). Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized with Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml−1 of Richelia were detected in the eastern basin, while small (0.7–1.5 μm) and large (2.5–3.2 μm) Nitro821-targeted cells were recovered at all stations and averaged 3.5 cell ml−1. The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. Surprisingly, the larger hybridized cells were not belonging to UCYN-B and C but to plastids of picoeukaryote. NifH gene was not recovered among picoeukaryotes, when rhizobia sequences, including the ones of Bradyrhizobia, were dominating nifH clone libraries from picoplanktonic size fractions. Few sequences of γ-proteobacteria were also detected in central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the development of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles and photosynthetic activity to acquire carbon for sustaining diazotrophy. Among UCYN further work will be necessary to understand their suggested role in plastid evolution.

Summary
Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: from the origin of plastids to the dominance of rhizobia

Excerpt
Bar Zeev, E., Yogev , T., Man-Aharonovich, D., Kress, N., Herut, B., Beja, O., and Berman-Frank, I.: Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea, ISME J., 2, 911–923, 2008.; Bhattacharya, D., Yoon, H. S., and Hackett, J. D.: Photosynthetic eukaryotes unite: endosymbiosis connects the dots, Bioessays, 25, 50–60, 2003.; Berman-Frank, I., Quigg, A., Finkel, Z. V., Irwin, A. J., and Haramaty, L.: Nitrogen-fixation strategies and Fe requirements in cyanobacteria, Limnol. Oceanogr., 52, 2260–2269, 2007.; Béthoux, J. P. and Copin-Montégut, G.: Biological fixation of atmospheric nitrogen in the Mediterranean Sea, Limnol. Oceanogr., 31, 1353–1358, 1986.; Biegala, I. C., Kennaway, G., Alverca, E., Lennon, J.-F., Vaulot, D., and Simon, N.: Identification of bacteria associated with dinoflagellates (Dinophyceae) Alexandrium spp. using tyramide signal amplification-fluorescent in situ hybridization and confocal microscopy, J. Phycol., 38, 404–411, 2002.; De Giorgi, C., Sialer, M. F., and Lamberti, F.: Formalin-induced infidelity in PCR-amplified DNA fragments, Mol. Cell. Probes, 8, 459–462, 1994.; Biegala, I. C., Cuttle, M., Mary, I., and Zubkov, M. V.: Hybridization of picoeukaryotes by eubacterial probes is widespread and may introduce bias in biodiversity researches or reveal intimate relationship between both types of organisms, Aquat. Microb. Ecol., 41, 293–297, 2005.; Biegala, I. C. and Raimbault, P.: High abundance of diazotrophic picocyanobacteria (<3 μm) in a Southwest Pacific coral lagoon, Aquat. Microb. Ecol., 51, 45–53, 2008.; Bonnet, S., Biegala, I. C., Dutrieux, P., Slemons, L. O., and Capone, D. G.: Nitrogen fixation in the western equatorial Pacific: rates, diazotrophic cyanobacterial size class distribution, and biogeochemical significance, Global Biogeochem. Cy., 23, GB3012, doi:10.1029/2008GB003439, 2009.; Bonnet, S., Grosso, O., and Moutin T.: Nitrogen fixation in the Mediterranean Sea: a major biogeochemical process during the stratified period?, in preparation, 2010.; Breitbarth, E., Oschlies, A., and LaRoche, J.: Physiological constraints on the global distribution of Trichodesmium – effect of temperature on diazotrophy, Biogeosciences, 4, 53–61, doi:10.5194/bg-4-53-2007, 2007.; Capone, D. G.: Benthic nitrogen fixation, in: Nitrogen in the marine environment, edited by: Carpenter, E. J. and Capone, D. G., Academic, 105–137, 1983.; Capone, D. G., Subramaniam, A., Montoya, J. P., Voss, M., Humborg, C., Johansen, A. M., Siefert, R. L., and Carpenter, E. J.: An extensive bloom of the N2-fixing cyanobacterium Trichodesmium erythraeum in the central Arabian Sea, Mar. Ecol. Progr. Ser., 172, 281–292, 1998.; Carpenter, E. J. and Janson, S.: Intracellular cyanobacterial symbionts in the marine diatom Climacodium frauenfeldianum (bacillariophyceae), J. Phycol., 35, 540–544, 2000.; Chen, Y., Zehr, J. P., and Mellon, M. T.: Growth and nitrogen fixation of the diazotrophic filamentous nonheterocystous cyanobacterium Trichodesmium sp. IMS 101 in defined media: evidence for a circadian rhythm, J. Phycol., 32, 916–923, 1996.; Church, M. J., Jenkins, B. D., Karl, D. M., and Zehr, J. P.: Vertical distributions of nitrogen-fixing phylotypes at Stn ALOHA in the oligotrophic North Pacific Ocean, Aquat. Microb. Ecol., 38, 3–14, 2005a.; Church, M. J., Short, C. M., Jenkins, B. D., Karl, D. M., and Zehr, J. P.: Temporal patterns of nitrogenase gene (nifH) expression in the oligotrophic North Pacific Ocean, Appl. Environ. Microbiol., 71, 5362–5370, 2005b.; Crombet, Y., Leblanc, K., Quéguiner, B., Moutin, T., Rimmelin, P., Ras, J., Claustre, H., Leblond, N., Oriol, L., and Pujo-Pay, M.: Deep silicon maxima in the stratified oligotrophic Mediterranean Sea, Biogeosciences Discuss., 7, 6789–6846, doi:10.5

 

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