Introduction 1980 1993 1998 2005 a 1986 1993 1995 1994 1998 2001 1997 2005 Porphyridium cruentum 1966 1976 2003 2005 2005 2001 2006 2005 1997 2004 2006 1996 1996 2007 Porphyridium cruentum Synechocystis Materials and methods Isolation of isolated PBSs and PBS-thylakoid membranes Porphyridium cruentum 2 −2 −2  1988 The PBS-membrane vesicles were prepared as described by Mustardy et al. (1992) with slight modifications. Cells were harvested by centrifugation (5000 g; 10 min), rinsed with 0.5 M potassium phosphate buffer (pH 7.0), and then suspended in SPC medium (0.5 M sucrose, citrate, 0.5 M potassium phosphate, 0.3 M potassium citrate, pH 7.0). After homogenization, the cells were broken in a French press at 4,000 psi in order to achieve large membrane sheets with minimal disturbance. The broken cell mixture was layered on a two-step sucrose gradient (1.0 M and 1.3 M) with the same buffer conditions as the cell suspension. After centrifugation for 30 min in a micro-centrifuge, the PBS-containing thylakoids were collected from the 1.0–1.3 M sucrose interface. Samples for imaging were prepared by placing glow-discharged, collodion-carbon-coated copper grids (200 mesh/inch) onto a droplet of sample solution for 10 min, excess liquid was then blotted off and the samples were fixed with 2% glutaraldehyde, followed by successive washes on three droplets of double-distilled water. Staining was achieved by placing the grid on a droplet of 2% uranyl acetate. Finally, the staining solution was blotted off. Electron microscopy − 2 1992 2000 2000 Results −2 2 1 2 1 P. cruentum 1984 2003 Fig. 1 Typical examples of negatively stained cyanobacterial membranes and associated phycobilisomes showing multiple ordered 2-D arrays under low-light conditions (left frame) and a random distributiom under high-light conditions (right frame) and the space bar equals 1 μm for the left frame and 400 nm for the right frame  2 2 2 2 2 Fig. 2 Porphyridium cruentum A B C E F G H  3 3 Fig. 3 A B Synechocystis PCC C D E Thermosynechococcus elongatus F G  3 3 Thermosynechococcus elongatus 3 3 Discussion Porphyridium cruentum. 3 1987 1992 3 1999 1996 2 P. cruentum P. cruentum 1993 1993 1989 P. cruentum 1989 P. cruentum 3 Electronic supplementary material Below is the link to the electronic supplementary material.
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