STUDIES OF THE LOCALIZATION, PHYSICOCHEMICAL PROPERTIES, 

 AND ACTION OF PHYCOCYANIN IN ANACYSTIS NIDULANS 



John A. Bergeron 



The "blue-green algae, classed as primitive monerans^ '' , repre- 

 sent the lowest level of organization known to possess a higher 

 plant type of photosynthesis. The role in photosynthesis of the 

 phycocyanin in these organisms is particularly interesting from 

 the point of viey of ultra structural biochemistry. It has "been 

 shown repeatedly\2"'7) that despite the primacy normally assigned 

 to chlorophyll, the light absorbed by phycocyanin is used more 

 efficiently for photosynthesis (equated with photosynthetic oxy- 

 gen evolution). This property is all the more intriguing since 

 Hill activity is very labile in these organisms; the loss being 

 correlated with the release of phycocyanin^^^ . Then too, it has 

 been observed that fluorescence at about 685 mn, attributed to 

 chlorophyll, is proportionately greater for wavelengths absorbed 

 by phycocyanin. French and Young(9) attributed the differential 

 to inactive absorption by carotenoids in the "Soret" region of 

 chlorophyll, but DuysensvB) concluded that the magnitude of the 

 difference observed by him was too great to be explained by 

 screening. Duysens proposed the existence of two pools of chloro- 

 phyll of about equal size; one containing fluorescent, photosyn- 

 thetically active chlorophyll in proximity to phycocyanin, the 

 other nonfluorescent, photosynthetically inactive and remote from 

 phycocyanin. 



We have studied the blue-green alga Anacystis nidulans in the 

 hope of obtaining a better understanding of these phenomena. 

 This unicellular organism is characterized by a high capacity for 

 photosynthetic oxygen evolution, minimal dark respiration and a 



feneration time, under favorable conditions, of about two hours 

 10^11). The organism is maintained in continuous culture in the 

 D medium(^^^ at 25° or 35° C in cylindrical growth chambers of 

 one cm light path thermostated by circulating water through inner 

 and outer jackets. The light source is a UO W daylight fluores- 

 cent tube located on the axis. The culture is kept turbulent by 

 the introduction of the gas mixture (1-5^ COg in air) via a med- 

 ium porosity frit located at the bottom to one side. 



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