IR Home
AME
Home
Editors
Forthcoming
Information
Subscribe
Journals
Home
MEPS
AME
CR
DAO
ESEP
ESR
Search
Subscribe
Book Series
EE Books
Top Books
ESEP Books
Order
EEIU Brochures
(pdf format)
Discussion Forums
Home
Research
IR Research
Institutions
International Ecology Institute
Eco-Ethics International Union
Foundation
Otto Kinne Foundation
![](../../../../images/pixel.gif) | ![](../../../../images/pixel.gif) |
AME 39:257-269 (2005)
|
Abstract
|
![](../../../../images/hline.gif)
Ecotypic variation in phosphorus-acquisition mechanisms within marine picocyanobacteria
L. R. Moore1,*,**, M. Ostrowski2,**, D. J. Scanlan2, K. Feren1, T. Sweetsir1
1Department of Biological Sciences, University of Southern Maine, 96 Falmouth St, Portland, Maine 04103, USA 2Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
*Email: lmoore@usm.maine.edu**These authors contributed equally to this work
![](../../../../images/hline.gif)
ABSTRACT: Prochlorococcus and Synechococcus are major prokaryotic primary producers in the oligotrophic oceans that may be affected by the climate-related increases in nitrogen fixation and subsequent phosphorus (P) limitation in some parts
of the oceans. Evidence that Prochlorococcus populations in the North Pacific subtropical gyre (NPSG) have increased over the past decades, possibly due to having a competitive advantage under conditions of P limitation, suggests aspects of their P
physiology that are important for dictating their in situ success. Here, we compared the physiology of P acquisition and response to P stress (indicated by alkaline phosphatase activity, APA) among isolates of Prochlorococcus and
Synechococcus representing different genotypic clades within the marine picophytoplankton lineage (sensu Urbach et al. 1998: J Mol Evol 46:188201). The 2 Synechococcus isolates examined (WH 8102 and WH 7803) can utilize a wide variety
of organic P sources. Of the 3 Prochlorococcus isolates examined, only the HLI genotype, MED4, is capable of growth on a variety of organic P sources. Under conditions of P starvation the 2 Synechococcus strains and Prochlorococcus
MED4 exhibit significant increases in APA, above their measurable constitutive activities. The genomes of the Synechococcus strains and Prochlorococcus MED4 indicate the presence of many P-uptake and -regulatory genes required under
conditions of P stress, including the phoA gene that encodes for an alkaline phosphatase enzyme. The other isolates of Prochlorococcus, HLII MIT 9312 and LLIV MIT 9313, have distinctly different P-stress responses. MIT 9312, which contains
the same P-uptake and -regulatory genes as MED4, except for psip1 and ptrA, has no constitutive APA, but does exhibit measurable, albeit very low, activity when P starved. MIT 9313, which lacks phoA and a functional phosphate-sensing
histidine kinase gene, phoR, exhibits low constitutive activity that decreases when the cells become P-starved. These results show variability in P utilization and in P-stress response between the 2 genera of marine unicellular cyanobacteria, and
marked differences among Prochlorococcus genotypes, implying that only certain eco/genotypes of these marine cyanobacteria will have an ecological advantage under conditions of P limitation in the oceans. This further points to the critical need to
continue developing genotypic- or cell-specific tools to assess the response of the picophytoplankton community to large-scale changes in nutrient conditions in the oceans.
KEY WORDS: Marine cyanobacteria · Prochlorococcus · Synechococcus · Phosphorus starvation · Alkaline phosphatase activity · APA
Full text in pdf format
![](../../../../images/hline.gif)
Published in AME Vol.
39, No. 3
(2005) on June 20
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2005
|