Biophysical Journal 6: 611-619 (1966)
© 1966 the Biophysical Society

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Transfer of the Excitation Energy in Anacystis nidulans Grown to Obtain Different Pigment Ratios

ABSTRACT

The blue-green alga, Anacystis nidulans, was grown in lights of different colors and intensities, and its absorption and fluorescence properties were studied. Strong orange light, absorbed mainly by phycocyanin, causes reduction in the ratio of phycocyanin to chlorophyll a; strong red light, absorbed mainly by chlorophyll, causes an increase in this ratio. This confirms the earlier findings of Brody and Emerson (12) on Porphyridum, and of Jones and Myers (8) on Anacystis. Anacystis cultures grown in light of low intensity show, upon excitation of phycocyanin, emission peaks at 600 mµ and 680 mµ, due to the fluorescence of phycocyanin and chlorophyll a, respectively. Changes in the efficiency of energy transfer from phycocyanin to chlorophyll a are revealed by changes in the ratios of these two bands. A decrease in efficiency of energy transfer from phycocyanin to chlorophyll a seems to occur whenever the ratio of chlorophyll a to phycocyanin deviates from the normal. Algae grown in light of high intensity show, upon excitation of phycocyanin, only a fluorescence band at 660 mµ and no band at 680 mµ. This suggests reduced efficiency of energy transfer from phycocyanin to the strongly fluorescent form of chlorophyll a (chlorophyll a₂) and perhaps increased transfer to the weakly fluorescent form of chlorophyll a (chlorophyll a₁).