Abstract: | Homocontinuous cultures of the cyanobacterium Anacystis nidulans (syn. Synechococcus sp. PCC 6301) were grown at white light intensities of 2 and 20 W/m2, and supplied with 0.03 and 3 % CO2 enriched air. The mutual influence of these growth factors on the development of the photosynthetic apparatus was studied by analyses of the pigment content, by low temperature absorbance and fluorescence spectroscopy, by analyses of oxygen evolution light-saturation curves, and by SDS PAGE of isolated phycobilisomes. The two growth factors, light and CO2, distinctly affect the absorption cross section of the photosynthetic apparatus, which is expressed by its pigment pattern, excitation energy distribution and capacity. In response to low CO2 concentrations, the phycocyanin / allophycocyanin ratios were lower and one linker polypeptide L30R, of the phycobilisomes was no longer detectable in SDS PAGE. Apparently, low CO2 adaptation results in shorter phycobilisome rods. Specifically, upon adaptation to low light intensities, the chlorophyll and the phycocyanin content on a per cell basis increase by about 50% suggesting a parallel increase in the amount of phycobilisomes and photosystem core-complexes. Low light adaptation and low CO2 adaptation both cause a shift of the excitation energy distribution in favor of photosystem I. Variations in the content of the “anchor” polypeptides L60CM and L75CM are possibly related to changes in the excitation energy transfer from phycobilisomes to the photosystem II and photosystem I core-complexes. |