Bioluminescence is referred to organisms that are capable of generating light. The terms such as fluorescence, phosphorescence or chemiluminescence apply to the production of light from chemicals but bioluminescence is only similar to chemiluminescence ( a common term for generation of light when the energy for excitation has come from a chemical reaction in contrast to the absorption of photons as in fluorescence). Bioluminiscence is a type of chemiluminiscence where light generating chemical reaction occurs inside an organism. A wide range of organisms are gifted with the ability to produce light and to exhibit and manage it in a variety of ways. Bioluminescence in the oceans is exhibited by an extraordinary variety of creatures from bacteria and unicellular protists to squid and fish. Terrestrial organisms include certain arthropods, centipedes, annelids, millipedes, a terrestrial mollusc and some fungi. Luminiscence is normally generated by the organism by itself and not oftenly due to bacterial symbionts. Based on the chemical mechanisms known, studies signify that luminescence has independently evolved more than forty times.

Luminiscence is generated by most bioluminescent organisms when a chemical compound known as luciferin reacts with O2 to produce light and oxyluciferin. The chemical reaction among luciferin and oxygen is catalysed by the enzyme luciferase. Luciferases as luciferins generally have dissimilar structures in different variety of organisms. In supplementation to these other molecules known as cofactors need to be present for the bioluminescence reaction to continue (cofactors are molecules needed for the enzyme to carry out its catalytic action). The usual cofactors that are necessary for reactions of bioluminescence are Adenosine triphosphate(ATP) and calcium.
Because bioluminescence is seen in so many variety of organisms it is found to serve many different functions, however many functions still remain unknown. Both defensive and offensive strategies include;

• Surprise the predator - when a bright flash is produced at close range, bioluminescence is believed to stratle the predators causing them to hesitate.
• Smoke screen or mislead the predator - when secreted the display may take the function of a smoke screen (a cloud of glowing fluid that causes a situation hard for the predator to track the position of its escaping victim).
• Counterillumination - This form of disguise involves utilizing ventral (lower) photophores to match the dim light coming from the surface thus making a potential shadow disappear.
• Sacrifical tag - In this condition an organism may lose part of its body to predatoryattack. The lost tissues can continue to luminate for hours after even inside the predator's stomach.
• Burglar alarm - similar to the logic of sacrifical tag, it is an indirect effect of an organisms bioluminescence whereby predators become susceptible to attack from higher order predators.
• Aposematism - on land, it is generally accepted that brilliant coloration can publicize toxicity.
• Illumination - use of bright light by a predator to startle or perplex the prey.
• Intraspecific communication - communication inside species is a familiar purpose of bioluminescence in terrestrial firefly courtship.
• Attraction of mate and identification

Some Biological Applications of Bioluminiscence include

- Luciferin and luciferase enzyme can be utilized to find out the concentrations of vital biological molecules such as ATP and calcium. A known quantity of luiciferin and luciferase are added to blood or tissue sample, the cofactor concentrations can be determined from the intensity of the light emitted.

- Bioluminescent reactions can be used to quantify particular molecules that do not directly take part in the bioluminescence reaction. In this luciferase is attached to antibodiy molecules. Then the complex of antibody and luciferase is mixed with the analyte where it attaches to the molecule to be quantified. Then the mixture is washed to remove unbound antibodies, the molecule of interest can be quantified indirectly by adding luciferin and measuring the emission of light. These methods of quantification are termed as assays.

- Luciferase is frequently utilized as a "reporter gene" to study how individual genes are activated to generate protein or repressed to stop generating the protein.

- Recent studies signify that luciferase has been utilized to study infections of bacteria and virus in living animals and to identify bacterial adultration in food.

- Luciferase can be generated in the lab through genetic engineering for a variety of purposes by engineering luciferase genes into organisms of interest.

The prospect for the utilization of luciferase will keep on increasing.

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