by Sewwandi Rasanganie
Starting from micro scaled bacteria to very large animals like sharks, there are some fascinating creatures who can glow in different colours in the dark. These creatures can either produce light or emit light by two naturally occurring phenomenon known as bioluminescence and biofluorescence.
These colour illuminations improves the chances of survival of these animals in many ways. For camouflage, as warning colouration and as a part of escape strategies by confusing predators and prey luring are the major uses of bioluminescence to observe in animal world. However, when it comes to smaller organisms, the possible functions of bioluminescence are less clear. Scientists believe that bioluminescence of bacteria promotes symbiotic relationships with the host organisms that are lack in the ability to emit light themselves. In addition to that, there is another hypothesis that explains bioluminescence as an incidental trait in some organisms and that the emission of light is due to a byproduct of an essential metabolic function. However, according to the evolutionary history, continuous existence of bioluminescence can have direct or indirect advantage to the organism who bares it.
Bioluminescence refers to the ability of certain living organisms to produce and emit light by a chemical process happens in them. Since this reaction does not produce much heat, it is also called “cold light”.
Bioluminescent light is emitted in a range of wavelengths from 400(near infrared) to 720 nm(violet). Interestingly, wavelengths of bioluminescent light can be shifted depending on the habitat of the organism lives in. Accordingly, majority of bioluminescent marine organisms emit blue light (410–550 nm). Among them, from violet and blue (420–500 nm) in the deep sea and blue-green (460–520 nm) in shallow waters is more prominent. On the land, green-yellow (520–580 nm) wavelength is the most frequently observed range of light.
Fireflies are one of the most visible users of bioluminescence on land.
Fireflies produce light in special organs in their abdomens. A chemical called luciferin and enzymes called luciferases are involved in this reaction. In the presence of oxygen and ATP acting as the fuel for cellular work, light is produced. They control their flashing by regulating how much oxygen goes to their light-producing organs.
Not every animal that glows is bioluminescent. Some species only glow after absorbing light of shorter wavelength and emitting it in longer-wavelength and that process is called biofluorescence.
Biofluorescent organisms need to have special proteins built into their tissues to absorb energy from sunlight and re-emit in a different color. In the ocean, mostly blue light penetrates through the water and fluorescent organisms who live in ocean water can absorb that energy, and then emit light at a lower energy (such as green or red). Since observing biofluorescence require special equipment, sometimes biofluorescent animals can go unnoticed.
Currently, scientists are working on manipulating these biofluorescence related proteins in organisms to use in different technological applications such as smart crops. illuminating cities, fighting cancer, and find toxins in water.
With the smart crop idea, plants will change colour as red, yellow, or glowing green to “alert” the farmers when they are running out of water or nutrients, or when the plant is under stress due to a disease.
Bioluminescence is also frequently used in different types of assays due to the simplicity and sensitivity of bioluminescence assays which makes them easy to automate, especially for drug screening. It says that the activity of more than 100,000 compounds can be screened in a day using bioluminescence chemistry.
In addition to that, firefly bioluminescence reaction is used in pathogen detection. In this matter bioluminescent chemicals get activated by bacterial ATP and thereby, bacterial contaminations in food are identified by the resulted glow.
With the continuing research studies, applications for this incredible biological phenomenon will continue to grow in future.