Energization and Activation of Inorganic Carbon Uptake by Light in Cyanobacteria

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Abstract
The requirement of the inorganic carbon (Ci) transport system for light in cyanobacteria was investigated in Anabaena variabilis by the filtering centrifugation technique and in a mutant (E1) isolated from Anacystis nidulans using a gas exchange system. Ci transport capability increased with time of preillumination and decreased following darkening. Full activity could not be obtained by operating either photosystem II (PSII) or photosystem I alone. 3(3,4 Dichlorophenyl)-1,1 dimethylurea strongly inhibited Ci uptake. Very low activity of PSII was sufficient to activate Ci uptake. However, in the presence of dithiothreitol PSII activity was not required. We conclude that light may be required to activate as well as to energize Ci uptake in cyanobacteria.