Regulation of phosphate uptake kinetics inOscillatoria agardhii |
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Authors: | Roel Riegman Luuc R Mur |
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Institution: | (1) Laboratorium voor Microbiologie, Universiteit van Amsterdam, Nieuwe Achtergracht 127, NL-1018 WS Amsterdam, The Netherlands |
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Abstract: | In order to study phosphate uptake kinetics the cyanobacteriumOscillatoria agardhii was grown in continuous culture under a phosphorus limitation. The affinity of the uptake system reflected in the initial slope of the uptake rate versus external substrate concentration curve (dV/ds) was found to be unaffected by the growth wate.The maximum phosphate uptake rate (V
m
) decreased as the growth rate was increased. Attempts were made to relate the decrease ofV
m
to the increase in phosphorus content of the cells that occurred a higher growth rates. Accumulation of phosphate during pulse experiments indeed resulted in a decrease ofV
m
. However feedback regulation ofV
m
by accumulated phosphorus was found to occur only to a small extent in steady state growing cells. The main part of the regulation of the activity of the phosphate uptake system seemingly is determined by a long term process that is, at least longer than 2 h. The presence of short term feedback inhibition by accumulated phosphorus on the activity of the uptake system provides an explanation of the phenomenon thatOscillatoria agardhii is not able to grow at near
max growth rates under a phosphorus limitation. |
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Keywords: | Cyanobacterium Phosphate Uptake Kinetics Regulation Pulse Steady state |
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