| Traffic lights in trichodesmium. Regulation of photosynthesis for nitrogen fixation studied by chlorophyll fluorescence kinetic microscopy. | |
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MedLine Citation:
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PMID: 15299119 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We investigated interactions between photosynthesis and nitrogen fixation in the non-heterocystous marine cyanobacterium Trichodesmium IMS101 at the single-cell level by two-dimensional (imaging) microscopic measurements of chlorophyll fluorescence kinetics. Nitrogen fixation was closely associated with the appearance of cells with high basic fluorescence yield (F(0)), termed bright cells. In cultures aerated with normal air, both nitrogen fixation and bright cells appeared in the middle of the light phase. In cultures aerated with 5% oxygen, both processes occurred at a low level throughout most of the day. Under 50% oxygen, nitrogen fixation commenced at the beginning of the light phase but declined soon afterwards. Rapid reversible switches between fluorescence levels were observed, which indicated that the elevated F(0) of the bright cells originates from reversible uncoupling of the photosystem II (PSII) antenna from the PSII reaction center. Two physiologically distinct types of bright cells were observed. Type I had about double F(0) compared to the normal F(0) in the dark phase and a PSII activity, measured as variable fluorescence (F(v) = F(m) - F(0)), similar to normal non-diazotrophic cells. Correlation of type I cells with nitrogen fixation, oxygen concentration, and light suggests that this physiological state is connected to an up-regulation of the Mehler reaction, resulting in oxygen consumption despite functional PSII. Type II cells had more than three times the normal F(0) and hardly any PSII activity measurable by variable fluorescence. They did not occur under low-oxygen concentrations, but appeared under high-oxygen levels outside the diazotrophic period, suggesting that this state represents a reaction to oxidative stress not necessarily connected to nitrogen fixation. In addition to the two high-fluorescence states, cells were observed to reversibly enter a low-fluorescence state. This occurred mainly after a cell went through its bright phase and may represent a fluorescence-quenching recovery phase. |
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Authors:
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Hendrik Küpper; Naila Ferimazova; Ivan Setlík; Ilana Berman-Frank |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2004-08-06 |
Journal Detail:
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Title: Plant physiology Volume: 135 ISSN: 0032-0889 ISO Abbreviation: Plant Physiol. Publication Date: 2004 Aug |
Date Detail:
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Created Date: 2004-08-24 Completed Date: 2004-12-16 Revised Date: 2010-09-20 |
Medline Journal Info:
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Nlm Unique ID: 0401224 Medline TA: Plant Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 2120-33 Citation Subset: IM |
Affiliation:
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Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, Universität Konstanz, D-78457 Konstanz, Germany. hk282@cornell.edu |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Chlorophyll
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biosynthesis Cyanobacteria / physiology*, radiation effects* Kinetics Microscopy, Fluorescence Models, Biological Nitrogen Fixation / physiology* Photosynthesis / physiology* |
| Chemical | |
Reg. No./Substance:
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1406-65-1/Chlorophyll |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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