561 



Lawrence Bogorad, Frank V. Mercer, and Rosemary Mullens 



(2 8") 

 unit membrane structure ' 



Cytoplasmic photosynthetic lamellae 



Some photosynthetic pigments of the blue-green algae are 

 associated with lamellae and after permanganate fixation, these 

 lamellae appear to be two unit membranes in close contact, the 

 dark bands measuring 20 A and 40 K in width and the light bands 

 35 A. in width . Measurements made on six blue-green genera 

 have confirmed this basic pattern of the cytoplasmic lamellae, 

 but the dimensions of the outer, dark and light bands are ca.30 A 

 and the inner dark band 60 A . These dimensions, therefore, 

 are very similar to those of the photosynthetic lamellae of non- 

 grana type chloroplasts of higher plants. The dark bands have 

 been interpreted to be protein and the light bands to be lipid in 

 association with- chlorophyll '. On the basis of studies of 

 energy transfer ' the phycobiliproteins are assumed t^nlje lo- 

 cated close to chlorophyll a in blue-green and red algae . The 

 basic molecular structure proposed for these lamellae therefore 

 is similar to the models proposed for the photosynthetic lamellae 

 of the higher plants^ '''\ 



Photosynthetic lamellae of Cyanidium caldarium 



The basic organization of the photosynthetic lamellae in the 

 grana-less chloroplast of Cyanidium caldarium , an organism of 

 undetermined taxonomic position, has been shown, by electron mi- 

 croscopy, to be similar to that of other photosynthetic lamellae 

 ^ . C. caldarium has-been obtained in a number of variously 

 pigmented mutant forms . These mutants, therefore, should 

 offer a way of assessing the importance of the pigments in deter- 

 mining the formation and basic molecular structure of the photo- 

 synthetic lamellae. The mutant forms examined by electron mi- 

 croscopy in the present study are described in Table 1. 



The cells were grown in a liquid medium with 1 percent glu- 

 cose at 43 ± Z^C. under fluorescent illumination of 150 to 500 

 ft-c. Growth was vigorous, and the cells were harvested after 4 

 or 5 days. For fixation the cells were centrifuged, and the pel- 

 let was resuspended in 2 percent buffered KMnO, fixative pH 7.2 

 (Veronal acetate, calcium and magnesium chloride 0.001 M, respec- 

 tively.) After 30 minutes the cells were washed briefly in water 

 before being dehydrated in an ethanol series: 40,70, 100 per 

 cent. The cells were then embedded in methacrylate (75 per cent 

 butyl, 25 per cent methyl, 0.05 per cent benzol peroxide polymer- 

 ized at 70°C.) Sections were prepared with a Porter-Blum micro- 

 tome using a diamond knife, and examined in a Siemens Elmiskop 



