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20 results on '"Gorbunov, M. Y."'

3. Nutrients limitation of primary productivity in the Southeast Pacific (BIOSOPE cruise)

Author

Bonnet , S., Guieu , C., Bruyant , F., Prášil , O., Van Wambeke , F., Raimbault , P., Grob , C., Moutin , T., Gorbunov , M. Y., Zehr , J. P., Masquelier , S. M., Garczarek , Laurence, Claustre , H., University of Southern California ( USC ), Laboratoire d'océanographie de Villefranche ( LOV ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Dalhousie University [Halifax], Institute of Microbiology ASCR, University of South Bohemia, Laboratoire d'océanographie et de biogéochimie ( LOB ), Université de la Méditerranée - Aix-Marseille 2-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Rutgers, The State University of New Jersey [New Brunswick] ( RUTGERS ), University of California [Santa Cruz] ( UCSC ), Station biologique de Roscoff [Roscoff] ( SBR ), and Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS )

Subjects
0106 biological sciences, [ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, 010504 meteorology & atmospheric sciences, 010604 marine biology & hydrobiology, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, [ SDU.STU ] Sciences of the Universe [physics]/Earth Sciences, 14. Life underwater, [ PHYS.ASTR.CO ] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 01 natural sciences, [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], 0105 earth and related environmental sciences
Abstract

Iron is an essential nutrient involved in a variety of biological processes in the ocean, including photosynthesis, respiration and nitrogen fixation. Atmospheric deposition of aerosols is recognized as the main source of iron for the surface ocean. In high nutrient, low chlorophyll areas, it is now clearly established that iron limits phytoplankton productivity but its biogeochemical role in low nutrient, low chlorophyll environments has been poorly studied. We investigated this question in the unexplored southeast Pacific, arguably the most oligotrophic area of the global ocean. Situated far from any continental aerosol source, the atmospheric iron flux to this province is amongst the lowest of the world ocean. Here we report that, despite low dissolved iron concentrations (~0.1 nmol l−1) measured across the whole gyre (3 stations situated in the center, the western and the eastern edge), photosynthesis and primary productivity are only limited by iron availability at the border of the gyre, but not in the center. The seasonal stability of the gyre has apparently allowed for the development of populations acclimated to these extreme oligotrophic conditions. Moreover, despite clear evidence of nitrogen limitation in the central gyre, we were unable to measure nitrogen fixation in our experiments, even after iron and/or phosphate additions, and cyanobacterial nifH gene abundances were extremely low compared to the North Pacific Gyre. The South Pacific gyre is therefore unique with respect to the physiological status of its phytoplankton populations.

Published
2007

5. Synthesis of iron fertilization experiments: From the Iron Age in the Age of Enlightenment

Author

Baar, H. J. W. de, Boyd, P. W., Coale, K. H., Landry, M. R., Tsuda, A., Assmy, Philipp, Bakker, D. C. E., Bozec, Y., Barber, R. T., Brzezinski, M. A., Buesseler, K. O., Boye, M., Croot, P. L., Gervais, F., Gorbunov, M. Y., Harrison, P. J., Hiscock, W. T., Laan, P., Lancelot, C., Law, C. S., Levasseur, M., Marchetti, A., Millero, F. J., Nishioka, J., Nojiri, Y., Oijen, T., Riebesell, U., Rijkenberg, M. J. A., Saito, H., Takeda, S., Timmermans, K. R., Veldhuis, M. J. W., Waite, A. M., Wong, C. S., Baar, H. J. W. de, Boyd, P. W., Coale, K. H., Landry, M. R., Tsuda, A., Assmy, Philipp, Bakker, D. C. E., Bozec, Y., Barber, R. T., Brzezinski, M. A., Buesseler, K. O., Boye, M., Croot, P. L., Gervais, F., Gorbunov, M. Y., Harrison, P. J., Hiscock, W. T., Laan, P., Lancelot, C., Law, C. S., Levasseur, M., Marchetti, A., Millero, F. J., Nishioka, J., Nojiri, Y., Oijen, T., Riebesell, U., Rijkenberg, M. J. A., Saito, H., Takeda, S., Timmermans, K. R., Veldhuis, M. J. W., Waite, A. M., and Wong, C. S.

Published
2005

20. Investigation of OCP-triggered dissipation of excitation energy in PSI/PSII-less Synechocystis sp. PCC 6803 mutant using non-linear laser fluorimetry.

Author

Kuzminov FI, Karapetyan NV, Rakhimberdieva MG, Elanskaya IV, Gorbunov MY, and Fadeev VV

Subjects
Darkness, Kinetics, Lasers, Models, Biological, Normal Distribution, Photochemical Processes radiation effects, Phycobilisomes metabolism, Phycobilisomes radiation effects, Spectrometry, Fluorescence, Synechocystis radiation effects, Thermodynamics, Time Factors, Bacterial Proteins metabolism, Fluorometry methods, Mutation genetics, Nonlinear Dynamics, Photosystem I Protein Complex metabolism, Photosystem II Protein Complex metabolism, Synechocystis metabolism
Abstract

In order to prevent photodestruction by high light, photosynthetic organisms have evolved a number of mechanisms, known as non-photochemical quenching (NPQ), that deactivate the excited states of light harvesting pigments. Here we investigate the NPQ mechanism in the cyanobacterium Synechocystis sp. PCC 6803 mutant deficient in both photosystems. Using non-linear laser fluorimetry, we have determined molecular photophysical characteristics of phycocyanin and spectrally distinct forms of allophycocyanin for the cells in non-quenched and quenched states. Our analysis of non-linear fluorescence characteristics revealed that NPQ activation leads to an ~2-fold decrease in the relaxation times of both allophycocyanin fluorescence components, F660 and F680, and a 5-fold decrease in the effective excitation cross-section of F680, suggesting an emergence of a pathway of energy dissipation for both types of allophycocyanin. In contrast, NPQ does not affect the rates of singlet-singlet exciton annihilation. This indicates that, upon NPQ activation, the excess excitation energy is transferred from allophycocyanins to quencher molecules (presumably 3'hydroxyechinenone in the orange carotenoid protein), rather than being dissipated due to conformational changes of chromophores within the phycobilisome core. Kinetic measurements of fluorescence quenching in the Synechocystis mutant revealed the presence of several stages in NPQ development, as previously observed in the wild type. However, the lack of photosystems in the mutant enhanced the magnitude of NPQ as compared to the wild type, and allowed us to better characterize this process. Our results suggest a more complex kinetics of the NPQ process, thus clarifying a multistep model for the formation of the quenching center., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Published
2012
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