562 



Lawrence Bogorad, Frank V. Mercer, and Rosemary Mullens 



1 at 80 kv. Electron micrographs were taken at 10,000 to 40,000 

 magnifications. 



Table 1 

 Strains of Cyanidium caldarium studied 



Strain Pigments present 



Wild-type-autotrophic Chlorophyll a., carotenoids, phycocyanin, 



allophycocyanin . 

 III-D-2 autotrophic As in wild-type but greater amounts of 



all pigments. 

 III-C autotrophic Chlorophyll a, carotenoids. 

 GGB heterotrophic Phycocyanin, allophycocyanin, carotenoids. 

 GGB-Y heterotrophic Carotenoids. 



Cells contain approximately 40% less chlorophyll a than wild- 

 type. Extracts of III-C cells do not react with antibody pre- 

 pared by immunizing rabbits with C. caldarium phycocyanin. 

 Therefore, this mutant most likely lacks the protein as well 

 as the bile pigment of phycocyanin. 



As can be seen from Figures 1,2,3,4,5 in all the types shown 

 the individual photosynthetic lamellae have the same basic pat- 

 tern consisting of two unit membranes in close contact. Occa- 

 sionally, in some sections, the unit membranes had separated 

 over short distances, showing clearly that the lamellae consist 

 of two unit membranes in close contact. The dimensions of each 

 unit membrane are similar to those that have been described for 

 the photosynthetic lamellae of the blue-green algae and certain 

 higher plants. Each unit membrane consists of two dark bands, 

 approximately 25 A - 30 A wide, separated by a light band approx- 

 imately 30 A wide. The structure of the unit membrane appears 

 to be independent of pigment composition. There are, however, 

 striking differences in the arrangement and amount of lamellar 

 system, and in chloroplast organization among the mutants examin- 

 ed (Figures 1,2,3,4,5) . 



In III-D-2, wild-type, and III-C strains, the mature chloro- 

 plasts are well formed, of similar sizes, and enclosed by a dis- 

 tinct limiting membrane. The main difference appears to be in 

 the number of lamellae present. Of these three strains, cells 

 of mutant III-D-2 (Figure 1) contain the highest concentration 

 of all three pigments; they also have the greatest number of la- 

 mellae per chloroplast and the most highly organized chloro- 

 plasts. Mature cells of wild-type (Figure 2) closely resemble 

 those of III-D-2, but their chloroplasts have fewer lamellae and 



