Bioluminescent bacteria: what a way to glow

We all love living things that glow in the dark, and scientists are no exception. Roger Tsien won a Nobel Prize in 2008 for discovering and developing green fluorescent protein and – perhaps even more excitingly – evil scientists turned mice fluorescent in a recent episode of the BBC television series Sherlock.

For animals that live in the blackness of the deep ocean, a little bit of bioluminescence goes a long way. For the squid Euprymna scolopes, this bioluminescence is generated by Vibrio fischeri bacteria that live within its light organ. The light organ is incredible, and it helps to hide the squid’s silhouette. This symbiosis is a win–win situation: the bacteria get housed and fed, and the squid gets a built-in cloaking device. Free-living bacteria also generate bioluminescence – but if they’re not in a symbiotic relationship, why do they bother?