Posted by: Glow-worm PJ17 OCT 2012
The term “bioluminescence” describes light produced within an organism by chemical reaction. It needs no energy from another source, unlike biofluorescence, in which proteins absorb external energy and reradiate it.
Most bioluminescent species are aquatic, often living at great ocean depths. It is estimated that up to 90 per cent of deep sea organisms emit some form of bioluminescence. Of the non-aquatic bioluminescent species, the most familiar are probably the firefly and glow-worm.
Bioluminescence tends to serve five main functions: camouflage, repulsion (of predators), attraction (of prey, or for mating purposes), communication (in some bacteria) and illumination.
The biological processes that produce luminescence are similar in aquatic and terrestrial organisms. A protein generically referred to as luciferin is oxidised in the presence of a catalyst called luciferase to produce oxyluciferin and light. Species variation in the structures of these proteins affects the colour of the emitted light.
Luciferins have found increasing applications in science and medicine, and biotechnology companies have already cloned and patented bioluminescent proteins. Among the bioluminescent proteins, luciferin and aequorin are the most commonly employed in scientific research. Aequorin is a bioluminescent protein complex obtained from certain jellyfish. It only emits its light in the presence of calcium ions, which, when they bind to the complex, cause it to release its luminescent molecule. The amount of light emitted can be used as an accurate measurement of calcium ions.
In experiments in mice, bioluminescent genes have been inserted into pathogenic bacteria, causing them to glow when luciferin is injected into the bloodstream. Similar procedures have been used to monitor the efficacy of antibiotics, with the glow caused by the pathogens being used as an indicator of bacterial numbers. It is also used in cancer research for monitoring tumour spread and response to treatment. The big advantage of these techniques is that treatment can be monitored in vivo, whereas conventional methods would require the mice to be killed and dissected.