Lipid diffusion in the thylakoid membranes of the cyanobacterium Synechococcus sp.: effect of fatty acid desaturation.

Thylakoid membranes are crucial to photosynthesis in cyanobacteria and plants. In cyanobacteria, genetic modification of membrane lipid composition strongly influences cold tolerance and susceptibility to photoinhibition. We have used fluorescence recovery after photobleaching to measure the diffusion of a lipid-soluble fluorescent marker in cells of the cyanobacterium Synechococcus sp. PCC 7942. We have compared the wild-type strain with a transformant with an increased level of fatty acid unsaturation. The transformant showed a six-fold increase in the diffusion coefficient for the fluorescent marker at growth temperature. This is the first direct measurement of lipid diffusion in a photosynthetic membrane.