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2-Methylhopanoids are maximally produced in akinetes of Nostoc punctiforme: geobiological implications

Doughty, D. M. and Hunter, R. C. and Summons, R. E. and Newman, D. K. (2009) 2-Methylhopanoids are maximally produced in akinetes of Nostoc punctiforme: geobiological implications. Geobiology, 7 (5). pp. 524-532. ISSN 1472-4677. http://resolver.caltech.edu/CaltechAUTHORS:20130417-105815720

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Abstract

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.


Item Type:Article
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http://dx.doi.org/10.1111/j.1472-4669.2009.00217.xDOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1111/j.1472-4669.2009.00217.x/abstractPublisherUNSPECIFIED
ORCID:
AuthorORCID
Newman, D. K.0000-0003-1647-1918
Additional Information:© 2009 Blackwell Publishing Ltd. Received 11 June 2009; accepted 04 September 2009. We thank Carolyn Colonero for assistance with mass spectrometric analysis. D. K. N. and R. E. S. are supported by the NASA Exobiology and Astrobiology Programs. D. K. N. is an Investigator of the Howard Hughes Medical Institute, which also supported D. M. D.
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Funding AgencyGrant Number
NASA Exobiology ProgramUNSPECIFIED
NASA Astrobiology programUNSPECIFIED
Howard Hughes Medical InstituteUNSPECIFIED
Record Number:CaltechAUTHORS:20130417-105815720
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130417-105815720
Official Citation:DOUGHTY, D. M., HUNTER, R. C., SUMMONS, R. E. and NEWMAN, D. K. (2009), 2-Methylhopanoids are maximally produced in akinetes of Nostoc punctiforme: geobiological implications. Geobiology, 7: 524–532. doi: 10.1111/j.1472-4669.2009.00217.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37989
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:17 Apr 2013 23:50
Last Modified:24 Oct 2017 15:54

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