All of us have come across a golden- glowing firefly or the luminescent blue ocean waves at night. We also have been fascinated to see how deep sea creatures have their own light source, their own natural flashlights to help them navigate the deep waters. All these creatures possess a unique biological property called bioluminescence- the ability to produce visible light by biochemical reactions.
In all these creatures, there exists a specific oxidative enzyme, which oxidises a substrate, releasing light. This conversion of chemical energy to radiant energy is very efficient, with negligible heat production, so this emission is also called "cold light". This enzyme is universally known as luciferase, and its substrate as luciferin.
In all these creatures, there exists a specific oxidative enzyme, which oxidises a substrate, releasing light. This conversion of chemical energy to radiant energy is very efficient, with negligible heat production, so this emission is also called "cold light".
Depending on the source organism, they are termed as firefly luciferin, bacterial luciferin and so on. The actual chemical composition of both the enzyme and the substrate, varies considerably from one organism to another.
Most bioluminescent creatures make their own luciferin. However, some creatures get it through symbiotic relations. For instance, some squid species form a symbiosis with bioluminescent bacteria, who actually produce the chemicals. The squid's body which harbours these bacteria appears to glow.
In all these cases, the luciferase enzyme brings about the oxidation of luciferin. This produces a high- energy, excited substance called oxyluciferin. This excited compound emits radiation in the range of visible light, to return to ground state. The wavelength of radiation emitted varies between organisms, and therefore the colour of light seen also shows slight variations. The mode of oxidising luciferin also differs, and it may or may not require ATP. These factors also determine the wavelength of the emitted radiation.
Besides being a natural wonder, this enzyme- catalysed reaction is a matter of great research interest and its kinetics and regulation is being widely studied. The mechanism of bioluminescence has also been replicated artificially in labs to act as a visual indicator of a biochemical reaction.
With increasing levels of pollution and climate change, these wonderful bioluminescent creatures are being threatened. While we attempt to illuminate our lives, we should take care to preserve these creatures and their habitats, so that they can continue to brighten up nature.
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