8 Detection of Rhythmic Bioluminescence From Luciferase Reporters in Cyanobacteria

The unicellular cyanobacterium Synechococcus elongatus PCC 7942 is the model organism for studying prokaryotic circadian rhythms. Although S. elongatus does not display an easily measurable overt circadian behavior, its gene expression is under circa-dian control; hence, a “behavior ” is created by linking a cyanobacterial promoter to either the bacterial luxAB or firefly luc luciferase genes to create reporter fusions whose activity can be easily monitored by bioluminescence. Numerous vectors have been cre-ated in our lab for introducing luciferase reporter genes into the S. elongatus chromo-some. A choice of methods and equipment to detect light production from the luciferase fusions provides a means for high-throughput, automated mutant screens as well as test-ing rhythms from two promoter fusions within the same cell culture. Key Words: Synechococcus elongatus PCC 7942; cyanobacteria; luciferase; biolu-minescence; circadian rhythm; neutral site