Fig 2.

Heterocyst formation in Anabaena PCC 7120 wild type and amiC mutant strains SR477 and SR478. (A) Thin-layer chromatography of lipid extracts of filaments of Anabaena PCC 7120 wild type (WT) and amiC mutant strains SR477 and SR478 grown in NH₄Cl (+) and after 48 h of N step-down (−). Stars indicate the positions of the two heterocyst-specific glycolipids. (B) Light micrographs of alcian blue-stained filaments after incubation for 48 h on N₂. (C) Transmission electron micrographs of ultrathin sections of Anabaena PCC 7120 wild type and amiC mutant strains SR477 and SR478 incubated for 48 h in nitrogen-free medium. Magnification of the boxed area is shown on the lower right. Bar = 10 μm (B) and 1 μm (C).