The natural phenomenon of bioluminescence is the emission of visible light by living organisms mediated by an enzyme-catalysed (‘luciferase’) reaction of molecular oxygen with a substrate (‘luciferin’). Bioluminescent organisms are diverse and widely distributed in nature, for example bacteria, dinoflagellates, fungi and insects. The luciferases show no homology to each other and the luciferins are also chemically unrelated. Molecular oxygen is the only common feature of bioluminescence reactions, indicating that the luminescent systems in most organisms may have evolved independently (Wilson & Hastings, 1998).