Cell Biology of Cyanobacteria
Conrad Mullineaux
Professor of Microbiology
School of Biological and Chemical Sciences
Queen Mary, University of London
Mile End Road,
London E1 4NS
UK
The cyanobacterium Synechocystis 6803 is a favourite model organism for genetic manipulation. It is naturally transformable, it can grow heterotrophically as well as phototrophically, and it was the first photosynthetic organism to have its genome completely sequenced. It has roughly spherical cells about 2 - 3.5 microns across
Thin-section electron micrograph of Synechocystis 6803. Note the thylakoid membranes (irregular loops of membrane in the cytoplasm). The dark spots on the membrane surface are phycobilisomes.
Scanning electron micrographs of Synechocystis 6803. All electron micrographs courtesy of Anna Law and Iain Wilson, NIMR Mill Hill
Although Synechocystis cells are relatively small, it is still possible to use fluorescence microscopy to get information on the distribution of cell components in living cells.
Confocal fluorescence micrographs of Synechocystis cells in which the FtsH (slr0228) protease has been tagged by gene fusion. Scale-bars are 5 microns. Green fluorescence is from GFP, red fluorescence is from the photosynthetic pigments in the thylakoid membranes and a merged image is shown below. The overlap of red and green fluorescence shows that FtsH is located in the thylakoids, where it plays a key role in the repair of Photosystem II. Collaboration with Myles Barker and Peter Nixon (Imperial college) Ref: Komenda et al (2006).
Confocal fluorescence images of Synechocystis cells expressing GFP fused to a TAT signal sequence (collaboration with Colin Robinson, University of Warwick). GFP fluorescence in green, fluorescence from the photosynthetic pigments in red. A merged image is shown on the right. The TAT pathway exports GFP to the periplasm (shown by the green "halo" of fluorescence surrounding the cytoplasm). Ref: Spence et al (2003)
Some key publications on this topic:
Spence, E., Sarcina, M., Ray, N., Møller S.G., Mullineaux, C.W.and Robinson, C. (2003) Membrane-specific targeting of green fluorescent protein by the Tat pathway in the cyanobacterium Synechocystis PCC6803. Mol Microbiol. 48, 1481-1489.
Komenda, J., Barker, M., Kuvikova, S., De Vries, R., Mullineaux, C.W., Tichy, M. and Nixon, P.J. (2006) The FtsH protease, slr0228, is important for quality control of the thylakoid membrane of Synechocystis PCC6803. J. Biol. Chem. 281, 1145-1151.
