Acclimation of Trichodesmium erythraeum ISM101 to high and low irradiance analysed on the physiological, biophysical and biochemical level

Authors

  • Elisa Andresen,

    1. Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D78457 Konstanz, Germany
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  • Jens Lohscheider,

    1. Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D78457 Konstanz, Germany
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  • Eva Šetlikova,

    1. Faculty of Science and Institute of Physical Biology, University of South Bohemia, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic
    2. Department of Autotrophic Microorganisms, Institute of Microbiology, Academy of Sciences of the Czech Republic, Opatovický Mlýn, CZ-37981 Třeboň, Czech Republic
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  • Iwona Adamska,

    1. Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D78457 Konstanz, Germany
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  • Miloslav Šimek,

    1. Biology Centre AS CR, v. v. i. Institute of Soil Biology and Faculty of Science, University of South Bohemia, Na Sadkach 7, CZ-37005 České Budějovice, Czech Republic
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  • Hendrik Küpper

    1. Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D78457 Konstanz, Germany
    2. Faculty of Science and Institute of Physical Biology, University of South Bohemia, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic
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  • A tribute in memory of our friend Ivan Šetlík (1928–2009).

Author for correspondence:
Hendrik Küpper
Tel: +49 7531 884112
Email: hendrik.kuepper@uni-konstanz.de

Summary

  • As the nonheterocystous diazotrophic cyanobacterium Trichodesmium lives both at the ocean surface and deep in the water column, it has to acclimate to vastly different irradiances. Here, we investigate its strategy of light acclimation in several ways.
  • In this study, we used spectrally resolved fluorescence kinetic microscopy to investigate the biophysics of photosynthesis in individual cells, analysed cell extracts for pigment and phycobiliprotein composition, measured nitrogenase activity and the abundance of key proteins, and assayed protein synthesis/degradation by radioactive labelling.
  • After acclimation to high light, Trichodesmium grew faster at 1000 μmol m−2 s−1 than at 100 μmol m−2 s−1. This acclimation was associated with decreasing cell diameter, faster protein turnover, the down-regulation of light-harvesting pigments and the outer part of the phycobiliprotein antenna, the up-regulation of light-protective carotenoids, changes in the coupling of phycobilisomes to the reaction centres and in the coupling of individual phycobiliproteins to the phycobilisomes. The latter was particularly interesting, as it represents an as yet unreported light acclimation strategy.
  • Only in the low light-acclimated culture and only after the onset of actinic light did phycourobilin and phycoerythrin contribute to photochemical fluorescence quenching, showing that these phycobiliproteins may become quickly (in seconds) very closely coupled to photosystem II. This fast reversible coupling also became visible in the nonphotochemical changes of the fluorescence quantum yield.

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