Document Detail

2-Methylhopanoids are maximally produced in akinetes of Nostoc punctiforme: geobiological implications.
MedLine Citation:
PMID:  19811542     Owner:  NLM     Status:  MEDLINE    
2-Methylhopanes, molecular fossils of 2-methylbacteriohopanepolyol (2-MeBHP) lipids, have been proposed as biomarkers for cyanobacteria, and by extension, oxygenic photosynthesis. However, the robustness of this interpretation is unclear, as 2-methylhopanoids occur in organisms besides cyanobacteria and their physiological functions are unknown. As a first step toward understanding the role of 2-MeBHP in cyanobacteria, we examined the expression and intercellular localization of hopanoids in the three cell types of Nostoc punctiforme: vegetative cells, akinetes, and heterocysts. Cultures in which N. punctiforme had differentiated into akinetes contained approximately 10-fold higher concentrations of 2-methylhopanoids than did cultures that contained only vegetative cells. In contrast, 2-methylhopanoids were only present at very low concentrations in heterocysts. Hopanoid production initially increased threefold in cells starved of nitrogen but returned to levels consistent with vegetative cells within 2 weeks. Vegetative and akinete cell types were separated into cytoplasmic, thylakoid, and outer membrane fractions; the increase in hopanoid expression observed in akinetes was due to a 34-fold enrichment of hopanoid content in their outer membrane relative to vegetative cells. Akinetes formed in response either to low light or phosphorus limitation, exhibited the same 2-methylhopanoid localization and concentration, demonstrating that 2-methylhopanoids are associated with the akinete cell type per se. Because akinetes are resting cells that are not photosynthetically active, 2-methylhopanoids cannot be functionally linked to oxygenic photosynthesis in N. punctiforme.
D M Doughty; R C Hunter; R E Summons; D K Newman
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2009-10-07
Journal Detail:
Title:  Geobiology     Volume:  7     ISSN:  1472-4669     ISO Abbreviation:  Geobiology     Publication Date:  2009 Dec 
Date Detail:
Created Date:  2009-11-17     Completed Date:  2010-01-12     Revised Date:  2013-05-31    
Medline Journal Info:
Nlm Unique ID:  101185472     Medline TA:  Geobiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  524-32     Citation Subset:  IM    
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
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MeSH Terms
Cell Membrane / chemistry
Molecular Structure
Nostoc / chemistry,  growth & development*,  metabolism*
Triterpenes / metabolism*
Grant Support
//Howard Hughes Medical Institute; //Howard Hughes Medical Institute
Reg. No./Substance:
0/Triterpenes; 471-62-5/hopane

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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