Shedding more light on bioluminescence

Bioluminescence is the emission of light from a biological organism and was wonderfully introduced from a Ted talk by Edith Widder (if you haven’t seen it you can find the link here). The idea of this blog post was to dive deeper into bioluminescence and provide some more information on this amazing and beautiful process.

The first question you may have is, “how is the light produced?” and the answer to this is chemistry. It is all due to a molecule called luciferin and an enzyme known as luciferase. Luciferase causes the reaction of oxygen with luciferin which produces energy released as a flash of light.

A wide diversity of organisms were shown during Widder’s talk, ranging from eels to single celled marine plants (dinoflagellates), and indeed bioluminescence is widespread in nature. From bacteria (such as found in the lure of deep sea angler-fish) to the larger vampire squid of the deep ocean. An interesting fact is that, aside from a few exceptions, bioluminescence is absent from freshwater environments.

The deep sea angler fish (left) and vampire squid (right).

The reason why the container of dinoflagellates lit up when Widder gave it a good shake is due to the chemical reaction discussed above. The physical action on the outside membrane of the cell causes ions (such as calcium, sodium) to generate a chemical charge and the reaction of luciferin to produce light. This all happens within 12 milliseconds! Although the flash of light from 1 cell may not look like much, if we scale it down to the size of a dinoflagellate (about 0.5 millimetres) the light can be seen by a fish up to 5m away. That would be equivalent to a 2m human being seen 20km away by flashing light, pretty impressive if you ask me!

Most of the bioluminescent light emitted in the oceans is within the blue and green spectrum of light, particularly in the deep ocean, as shown in Edith Widder’s talk. There is a reason for this and it is to do with the properties of light. When light hits the surface of the ocean (or any body of water) the light is absorbed sequentially through different wavelengths (see diagram). Red is the first to be absorbed, followed by orange, yellow, green and finally blue. This is why when you look at water it appears blue as all other wavelengths have been absorbed. As red light would not penetrate to the deep ocean, organisms here have not evolved to detect red light, so emitting red light to distract your predator would have no real effect here.

Finally, someone may ask “this is all great, but what has bioluminescence ever done for humanity?” Well, a small molecule known as green-fluorescent protein (GFP) was discovered and isolated from a jellyfish (Aequorea victoria) in 1962. This molecule (and others) have revolutionised biology. By attaching GFP to proteins it is possible to look at the movements and fates of compounds within cells. It is used to look at gene activation within cells and visualise growing tumours. In fact GFP has had such a profound impact on science that in 2008 the Nobel Prize in Chemistry was awarded to the discoverers of this molecule.

Image of the jellyfish Aequorea victoria and GFP-tagged keratin in a culture of skin (epithelial) cells

There are still many mysteries surrounding bioluminescence, but I hope this has been provided you with a little bit more information. If you have any further questions please ask in the comments section and we will try to answer them.

Many fun facts were taken from “Bioluminescence in the Sea, Haddock S., Moline M.A., Case, J.F. Ann. Rev. Mar. Sci. 2010”.

Information on the Nobel Prize awarded to Osamu Shimomura, Martin Chalfie and Roger Y. Tsein can be found here.

Dinoflagellates on the beach image: http://www.techeblog.com/index.php/tech-gadget/5-amazing-bioluminescent-things-that-actually-exist-in-nature

Image of the light absorbtion spectrum: http://www.seos-project.eu/modules/oceancolour/oceancolour-c01-p07.html