Document Detail

Activation of photosynthesis and resistance to photoinhibition in cyanobacteria within biological desert crust.
MedLine Citation:
PMID:  15466226     Owner:  NLM     Status:  MEDLINE    
Filamentous cyanobacteria are the main primary producers in biological desert sand crusts. The cells are exposed to extreme environmental conditions including temperature, light, and diurnal desiccation/rehydration cycles. We have studied the kinetics of activation of photosynthesis during rehydration of the cyanobacteria, primarily Microcoleus sp., within crust samples collected in the Negev desert, Israel. We also investigated their susceptibility to photoinhibition. Activation of the photosynthetic apparatus, measured by fluorescence kinetics, thermoluminescence, and low temperature fluorescence emission spectra, did not require de novo protein synthesis. Over 50% of the photosystem II (PSII) activity, assembled phycobilisomes, and photosystem I (PSI) antennae were detected within less than 5 min of rehydration. Energy transfer to PSII and PSI by the respective antennae was fully established within 10 to 20 min of rehydration. The activation of a fraction of PSII population (about 20%-30%) was light and temperature-dependent but did not require electron flow to plastoquinone [was not inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea]. The cyanobacteria within the crusts are remarkably resistant to photoinhibition even in the absence of protein synthesis. The rate of PSII repair increased with light intensity and with time of exposure. Consequently, the extent of photoinhibition in high-light-exposed crusts reached a constant, relatively low, level. This is in contrast to model organisms such as Synechocystis sp. strain PCC 6803 where PSII activity declined continuously over the entire exposure to high illumination. Ability of the crust's organisms to rapidly activate photosynthesis upon rehydration and withstand photoinhibition under high light intensity may partly explain their ability to survive in this ecosystem.
Yariv Harel; Itzhak Ohad; Aaron Kaplan
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-10-01
Journal Detail:
Title:  Plant physiology     Volume:  136     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  2004 Oct 
Date Detail:
Created Date:  2004-10-18     Completed Date:  2005-01-03     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3070-9     Citation Subset:  IM    
Department of Plant and Environmental Sciences , The Hebrew University of Jerusalem, Jerusalem 91014, Israel.
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MeSH Terms
Adaptation, Physiological / radiation effects
Chloramphenicol / pharmacology
Cyanobacteria / drug effects,  metabolism*,  radiation effects
Desert Climate*
Diuron / pharmacology
Dose-Response Relationship, Radiation
Photosynthesis / physiology*
Photosystem II Protein Complex / metabolism*
Protein Synthesis Inhibitors / pharmacology
Soil Microbiology*
Spectrometry, Fluorescence
Time Factors
Water / metabolism
Reg. No./Substance:
0/Photosystem II Protein Complex; 0/Protein Synthesis Inhibitors; 330-54-1/Diuron; 56-75-7/Chloramphenicol; 7732-18-5/Water

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