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Diel variations in the photosynthetic parameters of Prochlorococcus strain PCC 9511: Combined effects of light and cell cycle
Author(s) -
Bruyant F.,
Babin M.,
Genty B.,
Prasil O.,
Behrenfeld M. J.,
Claustre H.,
Bricaud A.,
Garczarek L.,
Holtzendorff J.,
Koblizek M.,
Dousova H.,
Partensky F.
Publication year - 2005
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2005.50.3.0850
Subject(s) - diel vertical migration , prochlorococcus , photosynthesis , quantum yield , biology , phytoplankton , carbon fixation , chlorophyll fluorescence , botany , axenic , synechococcus , biophysics , fluorescence , cyanobacteria , ecology , physics , genetics , optics , nutrient , bacteria
We examined the mechanisms related to the diel variations in the parameters of the relationship between the rate of carbon fixation of phytoplankton and irradiance ( P vs. E curve). Our goal was to understand what determines the phase of these variations relative to that of the light cycle. We grew the marine prokaryote Prochlorococcus in an axenic cyclostat culture system under a light–dark cycle that mimicked natural conditions at sea surface and followed changes in cell physiology with a 2‐h resolution. Individual cells divide mostly in phase with each other, once a day at the beginning of the dark period. The quantum yields of chlorophyll fluorescence, the maximum quantum yield of carbon fixation (φ Cmax ) and the maximum rate of carbon fixation (P B max ) exhibited diel variations over about factors of 2, 4, and 4, respectively, with maxima at the beginning of the light period. The morning drop in φ Cmax and the quantum yield of fluorescence, which was accompanied by only a small decrease (<15%) of photochemial efficiency of PSII ( F v / F m ), suggests regulation by light and preceded the drop in P B max by 4 h. The decrease in P B max during the day matched a decrease in the transcription level of Rubisco. The quantum yield of fluorescence, φ Cmax , and P B max increased again during the dark period, but this recovery was slowed at the time of cell division. Our results suggest that the pattern of diel variations in the photosynthetic parameters is determined both by photoacclimation and the cell‐division cycle.