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Glowing organisms that light up the waters!!
Some living things can light up dark places without help from the sun!

Life adapts in the most beautiful ways. Have you ever wondered watching the characters adorned with green lanterns, or shooting beams of red light, or escaping in a flash of blue or even a firefly emitting light? If yes, did you ever think, how can a living animal make light? The technical answer is that light is produced by energy released from chemical reactions either occurring inside or ejected by an organism.

This is the most beautiful and incredible phenomenon known as "Bioluminescence". It is nature’s chemical flashlight—lighting the dark inner reaches of remote caves, deep waters, and even moonless night skies with its eerily beautiful greenish glow. It is one of the ocean's most amazing natural phenomena. It seems to be drawn from science fiction or comic books, rather than science and natural history. Bioluminescence, though rarely seen in land organisms (with the noteworthy exception of the firefly) is extremely common for many marine creatures. Bioluminescent animals live primarily in regions of the ocean that don't get much sunlight. In the ocean, bioluminescence is not as rare as you might think. In fact, most types of animals, from bacteria to sharks, include some bioluminescent members.

While the functions of bioluminescence are not known for all animals, typically bioluminescence is used to warn or evade predators, to lure or detect prey, and for communication between members of the same species. Increasingly, scientists are taking our knowledge of bioluminescence, particularly in marine creatures, and finding new applications in chemistry, genetics, ecology and medicine. Let’s read on to know the sparkling facts of this phenomenon.

Bioluminescent creatures are found throughout marine habitats, from the ocean surface to the deep seafloor
What is bioluminescence?

Bioluminescence is an incredible and luminous phenomenon where light is produced by a chemical reaction within a living organism. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria and terrestrial invertebrates such as fireflies. Bioluminescence is a type of chemiluminescence, which is simply the term for a chemical reaction where light is produced. (Bioluminescence is chemiluminescence that takes place inside a living organism.)  All bioluminescent organisms use a reaction between an enzyme and a substrate to make light, but different species use different chemicals in the process. Let’s read the enzyme-substrate reaction that emits light, in detail in the next article – “How does bioluminescence work?”. The ability to emit light—bioluminescence—is both commonplace and magical. It is magical, because of its glimmering, captivating beauty. Commonplace, because many life-forms can do it.

Light is important element in deep-ocean environment because it is completely dark. Thus, bioluminescence may provide a survival advantage in the darkness of the deep sea, helping organisms find food, assisting in reproductive processes, and providing defensive mechanisms.

Fireflies use a well-understood chemical reaction controlled by their production of the enzyme Luciferase.
How does bioluminescence work?

The chemical reaction that results in bioluminescence requires two unique chemicals: luciferin and either luciferase or photoprotein. Luciferin is the compound that actually produces light. In a chemical reaction, luciferin is called the substrate. The bioluminescent color (yellow in fireflies, greenish in lanternfish) is a result of the arrangement of luciferin molecules. Luciferase is a generic term for the class of oxidative enzymes that produce bioluminescence, and is usually distinguished from a photoprotein. Luciferases are widely used in biotechnology, for microscopy  and as reporter genes, for many of the same applications as fluorescent proteins. However, unlike fluorescent proteins, luciferases do not require an external light source, but do require addition of luciferin, the consumable substrate. Thus, luciferase is an enzyme responsible for this incredible sparkling phenomenon. An enzyme is a chemical (called a catalyst) that interacts with a substrate to affect the rate of a chemical reaction. The interaction of the luciferase with oxidized (oxygen-added) luciferin creates a byproduct, called oxyluciferin. More importantly, the chemical reaction creates light. Thus, the light is the result of a chemical reaction between its enzyme form, luciferase, and some form of added energy (oxygen, sugar, etc.)

Most bioluminescent reactions involve luciferin and luciferase. Some reactions, however, do not involve an enzyme (luciferase). These reactions involve a chemical called a photoprotein. Photoproteins combine with luciferins and oxygen, but need another agent, often an ion of the element calcium, to produce light. Photoproteins were only recently identified, and biologists and chemists are still studying their unusual chemical properties. Photoproteins were first studied in bioluminescent crystal jellies found off the west coast of North America. The photoprotein in crystal jellies is called "green fluorescent protein" or GFP.

Bioluminescence in different colors!!
How many types of bioluminescence light?

The appearance of bioluminescent light greatly varies, depending on the habitat and organism in which it is found. Most marine bioluminescence, for instance, is expressed in the blue-green part of the visible light spectrum. These colors are more easily visible in the deep ocean. Also, most marine organisms are sensitive only to blue-green colors. They are physically unable to process yellow, red, or violet colors. Most land organisms also exhibit blue-green bioluminescence. However, many glow in the yellow spectrum, including fireflies and the only known land snail to bioluminesce, Quantula striata, native to the tropics of Southeast Asia. Few organisms can glow in more than one color. The so-called railroad worm (actually the larva of a beetle) may be the most familiar. The head of the railroad worm glows red, while its body glows green. Different luciferases cause the bioluminescence to be expressed differently. Some organisms emit light continuously. Some species of fungi present in decaying wood, for instance, emit a fairly consistent glow, called foxfire. Most organisms, however, use their light organs to flash for periods of less than a second to about 10 seconds. These flashes can occur in specific spots, such as the dots on a squid. Other flashes can illuminate the organism's entire body.

Thus, Bioluminescence does come in varied colors, from blue through red. The color is based on the chemistry, which involves a substrate molecule called luciferin, the source of energy that goes into light, and an enzyme called luciferase. In land animals such as fireflies and other beetles, the color is most commonly green or yellow, and sometimes red. In the ocean, though, bioluminescence is mostly blue-green or green. This is because all colors of light do not transmit equally through ocean water, so if the purpose of bioluminescence is to provide a signal that is detected by other organisms, then it is important that the light be transmitted through seawater and not absorbed or scattered. Blue-green light transmits best through seawater, so it is no surprise that this is the most common color of bioluminescence in the ocean.

Bioluminescence aids the survival and reproduction of individual organisms through such means as camouflage and defense, attraction of prey and mates, and communication
Why Bioluminescence?

Bioluminescence is used by organisms to hunt prey, defend against predators, find mates, and execute other vital activities. Many bioluminescent animals use the light they create the same way people use flashlights: to help them find their way and hunt for prey. Other bioluminescent animals have evolved to use their bioluminescence to act as a lure. Given the above scenarios of fish being hunted and captured because they are glowing in a dark environment, it seems counter-intuitive that some species of fish use bioluminescence as camouflage. In the ocean’s darkest depths, a fish has a difficult time seeing any objects beneath it, but it can more easily see fish that are above it because they are silhouetted against the light — small as it may be. Some species have developed areas of light on their undersides, which blurs their outlines and helps them blend into light coming from above. Thus, organisms use this phenomenon in multitude ways to survive in nature.

 Models of cancer spread can be studied through bioluminescence imaging
Applications of Bioluminescence in Biology and Medicine

Today, scientists and engineers are trying to harness the radiance of living things. Biologists and engineers are studying the chemicals and circumstances involved in bioluminescence to understand how people can use the process to make life easier and safer. Bioluminescent organisms are a target for many areas of research. Bioluminescence is a unique light source based on the luciferin-luciferase reaction, and their luciferases are good reporter enzymes in the field of bioresearch. Indeed, bioluminescence reporters are widely used in various aspects of biological functions, such as gene expression, post-translational modification, and protein-protein interaction in cell based assays. Using luciferase as an imaging reporter for cancer provides insight into cancer-specific molecular mechanisms within the context of the whole animal.  In addition, firefly luciferase has been used to locate primary tumors and their metastases in animal studies.

Although fluorescence imaging techniques that use fluorescent proteins (e.g., green fluorescent protein (GFP) and its derivatives) as probes have greatly contributed to the advancement of cell biology studies, bioluminescence imaging is emerging as a new and sensitive approach for understanding cell physiology. For example; Green fluorescent protein (GFP – isolated from Aequorea victoria in 1992, received the Nobel prize in chemistry in 2008), for instance, is a valuable "reporter gene". Reporter genes are chemicals (genes) that biologists attach to other genes they are studying. GFP reporter genes are easily identified and measured, usually by their fluorescence. This allows scientists to trace and monitor the activity of the studied gene—its expression in a cell, or its interaction with other chemicals.

Perhaps someday, when crops need water or nutrients, they’ll be able to tell farmers with a glow!!
Big ideas for Bioluminescence technology

Living light from fireflies, bacteria, and other luminescent creatures could change the way we illuminate our cities, fight cancer, and find toxins in our water. Bioluminescent trees, for instance, could help light city streets and highways. This would reduce the need for electricity. Bioluminescent crops and other plants could luminesce when they needed water or other nutrients, or when they were ready to be harvested. This would reduce costs for farmers and agribusiness.

  • Fields glow: Perhaps someday, when crops need water or nutrients, they’ll be able to tell farmers
  • Street-lights into treelights: One long-envisioned application for bioluminescence is to replace electricity-draining conventional streetlights, lit-up roads signs and interior lighting. Glowing fish could make for exotic pets, while trees that include bioluminescent genes could be used to illuminate roads and highways, or to provide Christmas trees that are truly green and don’t require electricity.
  • Some of the biotechnological companies, employ a luminescent marine bacterium in the Microtax assays that it uses to asses water quality. The bacteria glow diminishes when certain chemicals, such as heavy metals and pesticides, disrupt its light-making process. Bad bacteria in meat could be located, contaminated water could be flagged and monitored.
  • Illuminated candy: Candles can tickle our taste buds with citrusy sourness or cinnamon spiciness. But “Biolume” wants to make them do something new- light up!

References

  • https://www.nationalgeographic.org/encyclopedia/bioluminescence/
  • http://oceanexplorer.noaa.gov/explorations/09bioluminescence/background/bioluminescence/bioluminescence.html
  • https://scripps.ucsd.edu/labs/mlatz/bioluminescence/bioluminescence-questions-and-answers/
  • https://en.wikipedia.org/wiki/Luciferase
  • http://ngm.nationalgeographic.com/2015/03/luminous-life/judson-text
  • http://animals.howstuffworks.com/animal-facts/bioluminescence2.htm