How do cyanobacteria sense and respond to light?

Cyanobacteria exhibit numerous responses to changes in the intensity and spectral quality of light. What sensors do cyanobacteria use to detect light and what are the mechanisms of signal transduction? The publication in 1996 of the complete genome sequence of the cyanobacterium Synechocystis 6803 provided a tremendous stimulus for research in this field, and many light-sensors and signal transducers have now been identified. However, our knowledge of cyanobacterial light-signal transduction remains fragmentary. This review summarizes what we know about the ways in which cyanobacteria perceive light, some of the ways which they respond to light signals and some recent achievements in elucidating the signal transduction mechanisms. Some problems in characterizing cyanobacterial signal transduction pathways are outlined and alternative experimental strategies are discussed.