The rod-like structures containing ribosome particles isolated from cell membranes of the cyanobacterium Phormidium laminosum were sensitive to RNAase and capable to incoiporate in viíro ■'♦C-amino acids into polypeptides. These facts can be considered as an evidence for the presence of protein-synthesizing apparatus in the rod-like structures of cyanobacterial membranes.
Cell membranes of the cyanobacterium Phormidium lamino.sum were separated into two fractions by centrifugation in a stepwise sucrose gradient. One fraction contained mature thylakoid membranes and the other one contained membranes morphologically similar to primary membranes of pea etiochloroplasts. The latter ones represented an electron-transparent base with numerous electron-dense inclusions. The predominant type of the inclusions was rod-like structures containing presumably ribosomes.