Studies on the isolation and purification of chloroplasts from Euglena gracilis

Chloroplast DNA from three archegoniates

1. DNA from female and male Sphaerocarpos donnellii (liverwort) plants exhibits at least two species with buoyant densities of 1.703 (main band) and 1.691 (satellite) g cm(-3) in CsCl equilibrium gradients. At least part, if not all, of the satellite DNA is localized in plastids. It consists of up to 90% of uniformly sized circular molecules of an average circumference of 38.5 μm. Compared to other Chlorophyta, the liverwort's cpDNA is unusually low both in diensity and contour length. - 2. On the hand, cpDNA from the ferns Asplenium nidus and Pteris vittata resembles those of higher plants in buoyant density (1.697 g cm(-3)) and circumference (about 44.8 μm). - 3. Analysis of DNA from the archegoniate chloroplasts with restriction endonucleases indicates chat the cyclic molecules are monomers. - 4. The results show that the circular molecules found in cpDNA of higher plants do not represent the functionally required minimum size of DNA in plastids.

Nitrofuran-reducing enzymes of Euglena

Euglena gracilis strain Z, green, dark-brown, and "bleached" with N-methyl-N-nitro-N-nitrosoguanidine, was found to contain 2 soluble enzymes which reduce nitrofurans. A small amount of activity was demonstrated also in a particulate fraction of sonic extracts, but none in isolated chloroplasts. The reduction of 5 nitrofurans, having widely differing bleaching activities, by each of the 2 enzymes was examined.