Diel rhythmicity in amino acid uptake by Prochlorococcus
Mary, Isabelle, Garczarek, Laurence, Tarran, Glen A. , Kolowrat, Christian , Terry, Matthew J. , Scanlan, David J. , Burkill, Peter H. and Zubkov, Mikhail V. . (2008) Diel rhythmicity in amino acid uptake by Prochlorococcus. Environmental Microbiology, Vol.10 (No.8). pp. 2124-2131. ISSN 1462-2912
WRAP_Scanlan_8871765-090908-ZubkovDielRhythmsRev08ff.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://dx.doi.org/10.1111/j.1462-2920.2008.01633.x
The marine cyanobacterium Prochlorococcus, the most abundant phototrophic organism on Earth, numerically dominates the phytoplankton in nitrogen (N)-depleted oceanic gyres. Alongside inorganic N sources such as nitrite and ammonium, natural populations of this genus also acquire organic N, specifically amino acids. Here, we investigated using isotopic tracer and flow cytometric cell sorting techniques whether amino acid uptake by Prochlorococcus is subject to a diel rhythmicity, and if so, whether this was linked to a specific cell cycle stage. We observed, in contrast to diurnally similar methionine uptake rates by Synechococcus cells, obvious diurnal rhythms in methionine uptake by Prochlorococcus cells in the tropical Atlantic. These rhythms were confirmed using reproducible cyclostat experiments with a light synchronised axenic Prochlorococcus (PCC9511 strain) culture and 35S-methionine and 3H-leucine tracers. Cells acquired the tracers at lower rates around dawn and higher rates around dusk despite >104 times higher concentration of ammonium in the medium, presumably because amino acids can be directly incorporated into protein. Leucine uptake rates by cells in the S+G2 cell cycle stage were consistently 2.2 times higher than those of cells at the G1 stage. Furthermore, S+G2 cells up-regulated amino acid uptake 3.5 times from dawn to dusk to boost protein synthesis prior to cell division. Because Prochlorococcus populations can account from 13% at midday, and up to 42% at dusk, of total microbial uptake of methionine and probably of other amino acids in N-depleted oceanic waters, this genus exerts diurnally variable, strong competitive pressure on other bacterioplankton populations.
|Item Type:||Journal Article|
|Subjects:||Q Science > QL Zoology
Q Science > QR Microbiology
|Divisions:||Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)|
|Library of Congress Subject Headings (LCSH):||Cyanobacteria, Nitrogen, Circadian rhythms|
|Journal or Publication Title:||Environmental Microbiology|
|Official Date:||22 April 2008|
|Number of Pages:||8|
|Page Range:||pp. 2124-2131|
|Access rights to Published version:||Open Access|
Version accepted by publisher (post-print, after peer review, before copy-editing).
|Funder:||Natural Environment Research Council (Great Britain) (NERC)|
|Grant number:||NE/C514723/1 (NERC)|
Casey, J.R., Lomas, M.W., Mandecki, J., and Walker, D.E. (2007) Prochlorococcus contributes to new production in the Sargasso Sea deep chlorophyll maximum. Geophysical Research Letters 34: doi:10.1029/2006GL028725.
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