FIG. 4.

Progress of HGL synthesis and HGL layer formation. (A) Thin-layer chromatography of lipids of the wild-type Anabaena sp. strain before (lane 1) or at indicated times after (lanes 2 to 7) transfer to BG11₀ medium. (B and C) Representative transmission electron micrographs of ultrathin sections of filaments of the wild-type Anabaena sp. strain 14 h (B) or 20 h (C) after transfer to BG11₀ medium. The arrowhead in panel C indicates the HGL layer after 20 h. Bar = 1 μm. (D) The fluorescence of the NME-alr2887-GFP strain was determined, and the difference from the wild-type strain background for three independent measurements and three independent NME-alr2887-GFP clones is shown for the indicated times after nitrogen step-down. A.U., arbitrary units; ex, excitation; em, emission.