Iron limitation in the marine cyanobacterium Trichodesmium reveals new insights into regulation of photosynthesis and nitrogen fixation.
* As iron (Fe) deficiency is a main limiting factor of ocean productivity, its effects were investigated on interactions between photosynthesis and nitrogen fixation in the marine nonheterocystous diazotrophic cyanobacterium Trichodesmium IMS101. * Biophysical methods such as fluorescence kinetic microscopy, fast repetition rate (FRR) fluorimetry, and in vivo and in vitro spectroscopy of pigment composition were used, and nitrogenase activity and the abundance of key proteins were measured. * Fe limitation caused a fast down-regulation of nitrogenase activity and protein levels. By contrast, the abundance of Fe-requiring photosystem I (PSI) components remained constant. Total levels of phycobiliproteins remained unchanged according to single-cell in vivo spectra. However, the regular 16-kDa phycoerythrin band decreased and finally disappeared 16-20 d after initiation of Fe limitation, concomitant with the accumulation of a 20-kDa protein cross-reacting with the phycoerythrin antibody. Concurrently, nitrogenase expression and activity increased. Fe limitation dampened the daily cycle of photosystem II (PSII) activity characteristic of diazotrophic Trichodesmium cells. Further, it increased the number and prolonged the time period of occurrence of cells with elevated basic fluorescence (F(0)). Additionally, it increased the effective cross-section of PSII, probably as a result of enhanced coupling of phycobilisomes to PSII, and led to up-regulation of the Fe stress protein IsiA. * Trichodesmium survives short-term Fe limitation by selectively down-regulating nitrogen fixation while maintaining but re-arranging the photosynthetic apparatus.
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.|University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic.
Hendrik
H
Küpper
University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic.|Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic.
Ivan
I
Šetlík
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.
Sven
S
Seibert
University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic.|Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic.
Ondrej
O
Prášil
University of South Bohemia, Faculty of Biological Sciences and Institute of Physical Biology, Branišovská 31, CZ-370 05 České Budejovice, Czech Republic.|Academy of Sciences of the Czech Republic, Institute of Microbiology, Department of Autotrophic Microorganisms, Opatovický mlýn, CZ-37981 Třeboň, Czech Republic.
Eva
E
Šetlikova
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.
Martina
M
Strittmatter
Bar Ilan University, Mina and Everard Goodman Faculty of Life Sciences, Ramat Gan, 52900, Israel.
Orly
O
Levitan
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.
Jens
J
Lohscheider
Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.
Iwona
I
Adamska
Bar Ilan University, Mina and Everard Goodman Faculty of Life Sciences, Ramat Gan, 52900, Israel.
Ilana
I
Berman-Frank
D015153:Blotting, Western; D002338:Carotenoids / Q000378:metabolism; D049109:Cell Proliferation; D002734:Chlorophyll / Q000378:metabolism; D003470:Culture Media; D000458:Cyanobacteria / Q000166:cytology / Q000378:metabolism*; D015536:Down-Regulation; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D052979:Phycobiliproteins / Q000378:metabolism; D010799:Phycoerythrin / Q000378:metabolism
D003470:Culture Media; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D052979:Phycobiliproteins; D010799:Phycoerythrin; D002734:Chlorophyll; D002338:Carotenoids; D007501:Iron; D009591:Nitrogenase