Figure 7
Transmission electron microscopy (TEM) micrographs of the cell ultrastructure. (a) General view of a longitudinal section of a filament at low magnification, note the constrictions at cross cell walls - arrows; (b) Close-up of a longitudinal section evidencing typical cell inclusions of Cyanobacteria cells; (c) Dividing cells, note the different stages in the development of the cell wall invaginations - asterisks; (d) Detail of cell wall (Cw) and thylakoid membranes (Thy): I ≫ S-layer, II ≫ outer membrane, III ≫ periplasmatic space, IV ≫ peptidoglycan layer, V ≫ inner cytoplasmatic membrane106, between the thylakoids are numerous phycobilisomes (Phy) and ribosomes (Rhy); (e) Cell in cross-section where is visible the central nucleoplasmic region (Nc), the arrays of thylakoids and the mucilaginous sheath (Sh); (f) Close-up of the cell wall and the sheath (Sh) in cross-section, note the Oscillin fibrils (Osc) attached to the s-layer106,107; (g) Detail of the mucilaginous sheath with excreted exopolysaccharides (Eps); (h) fasciculate thylakoid membranes in longitudinal section, note the different directions of the membranes some were cut longitudinally and others were cut transversely - arrows; (i) Oblique section of the filaments, note the lipid droplets near the cross-walls and the cylindrical membrane structure that resembles “thylakoid centers” – arrow48,49; (j) Close-up of the oblique section evidencing the curved fascicules of thylakoids (arrow); (k) spherical formations of the thylakoid membranes - arrow; (l) spherical formations of the thylakoid membranes in high magnification - arrow. Lp – lipid droplet, Cb – carboxysomes/polyhedral bodies, Ph – polyphosphate granules, Cy – cyanophycin granules, Gy – electroyaline storage granule (glycogen granule), Ccw – cross-walls, Cw – Cell wall, Nc – nucleoplasmic region with DNA and ribosomes, Thy – thylakoid membranes, Rhy – Ribosomes, Phy – phycobilisomes, Sh – mucilaginous sheath.
