Uses of Bioluminescence

Uses of Bioluminescence

While chasing fireflies on warm summer nights, children rarely ponder more than which way the next bug will fly and where to keep their new-found friends after catching them. The glittering, light-producing insects often fascinate children and adults, but people seldom understand the reasons fireflies flicker. Bioluminescence is responsible for the blinking bugs as well as flashing fish, glinting glowworms, and the shimmering spores of fungus. In order to understand fully the benefits of bioluminescence one must first understand its purposes. Bioluminescence benefits organisms, and synthetic varieties are used more and more to benefit humans. Some natural purposes include: attracting a mate, attracting prey, camouflage, deterring predators, and aiding in hunting. Scientists are using bioluminescent organisms to synthetically trace the ATP and calcium in the cell, to illustrate progression of infection, and to assist in AIDS research.

It is necessary to understand the true definition of bioluminescence (organisms giving off light for their own benefit) is necessary in order to distinguish between bioluminescence and similar phenomena. Biological chemiluminescence and iridescence are sometimes confused with bioluminescence. An example of this would be the faint light produced when cells divide quickly, such as onion root tip cells undergoing mitosis. Since this resulting glow does not help the onion, it is not considered bioluminescence. Iridescence is different from bioluminescence because it is produced by reflection or refraction of an external light source. Although certain species of beetles and butterflies seem to shimmer, the beetle or butterfly does not produce this light; it comes from external sources such as the sun. 

The biological processes to produce bioluminescence are similar for creatures living on land and those in water. Although both terrestrial and aquatic bioluminescent organisms employ luciferin and luciferase to produce light, the structures of the luciferin and luciferase can be different depending on the organism. Luciferin is the broad name encompassing any material that glows when it loses electrons in the presence of luciferase. Luciferase is the enzyme that must be present to facilitate the oxidation (loss of electrons) of luciferin. Bioluminescent organisms produce diverse colors of light because their luciferin and luciferase are chemically different from each other. The color of the light produced depends on whether the organism is terrestrial or aquatic. Terrestrial organisms, such as fireflies and railroad worms, tend to produce red, yellow or green light. Aquatic organisms usually produce blue-green or green light because these colors travel well through the water without being absorbed, therefore enhancing the ability to be seen.

Found in marine, freshwater, and terrestrial environments, bioluminescent organisms are more prolific than most people think. While “more than half of all phyla in the animal kingdom contain members that are bioluminescent . . . [it] is most common in the sea, particularly in the deep ocean where the majority of species are luminescent”. Transmittance of bioluminescent light through water aids fish in finding mates and attracting prey. Since sunlight can only penetrate the uppermost layers of ocean depth, light signals among fish at great depths are quite successful ways to communicate. In fact, “in the deep ocean, where sunlight is dim or absent, more than 90% of the animals are luminescent”. Many of these creatures employ a symbiotic relationship with bioluminescent bacteria. The bacteria have a suitable environment and the creature can use the bioluminescence for its benefit. The “flashlight” fish, for example, houses bioluminescent bacteria in small pouches under its eyes. By opening and closing this pouch, the fish can use the light to communicate with other fish and to attract a mate.

Many species of fish use bioluminescence to help them find food. Angler fish are not themselves bioluminescent but have a unique way to attract prey. One of their dorsal fins has an adaptation that points forward and dangles in front of the mouth of the fish. This “lure” houses lustrous bacteria. A fish is drawn to what it thinks is glowing food, and the angler fish then eats the other fish as it tries to catch the lure. The shine of the lure attracts prey because fecal matter, a staple in the diet of many fish, glows while drifting down to the environment of the angler fish. Milius attributes the fecal glow to “the abundance of light-generating microbes in the diet of upper-ocean animals” 

One species of octopus also uses a glowing lure. The suckers of the Stauroteuthis syrtensis shine with a blue-green light. Researchers believe this attracts copepods (minuscule crustaceans) for the octopus. The octopus then catches copepods in mucus and sweeps them into the mouth.

Squid and black loose jaw fish use bioluminescence to capture prey. Squid have a symbiotic relationship with captured bioluminescent bacteria to aid in camouflage. By glowing softly, the squid erases its shadow caused by the moonlight shining into the sea. This allows the squid to move stealthily to attack its prey. The black loose jaw fish uses bioluminescence not to be seen, but to see prey. This fish produces a red light with a function similar to night vision goggles; the loose jaw can see prey but prey cannot detect the red light the fish produces. Terrestrial organisms also use bioluminescence to attract mates and aid in hunting. Fireflies may be the most well known bioluminescent land creature. Their blinking lights actually aid in communicating with each other to find a mate. On his bioluminescence web site, Marc Branham explains that “one or both sexes use a species specific flash pattern to attract a member of the opposite sex”. In one fascinating species of firefly, the female actually mimics the flash patterns of males of other species to attract them. She then consumes the male after he responds to her signals. The glowworm (a fly larva) “hangs in the middle of a web and emits a blue glow. Small winged insects are attracted to the glow, ensnared in the web, and devoured”.

Deterring predators is another natural use for bioluminescence. Dinoflagellates will light up when they are disturbed. This defense reaction can confuse the predator or bring attention to it in hopes that the predator will become the prey of other sea life. Experiments have been conducted to test the effectiveness of bioluminescent escape flashes. Researchers have found that glowing dinoflagellates have a better chance of escaping predators than those that lack bioluminescence. The “railroad worm” (the larval form of a beetle), named for its red, green and yellow flashes, uses bioluminescence as a warning to predators about its terrible taste.
Because of its successes in nature, humans are beginning to understand the significance bioluminescence can have in research queries. In an effort to combat water scarcity, biologists at Cambridge University are inserting genes from a bioluminescent jellyfish, aequorea victoria, into potatoes. Potatoes are often watered more frequently than necessary, wasting large water quantities because of the great demand of the crop in feeding the people of the planet. These engineered potatoes would glow when exposed to black light if they needed to be watered, allowing farmers to water only when necessary (Onion “One Potato, New Potato” 1). 

Bioluminescence research is also being conducted for use in the medical field. Virologist Christopher Contag and Pamela Contag have begun using bioluminescent bacteria to follow the progression of infection in mice. This process could reduce the number of mice used and killed for research, since the development of the disease can be traced while the animal is alive. Researchers inserted bioluminescent genes into salmonella bacteria, causing them to glow. They could watch as the infection spread and could judge which antibiotics were most effective by observing the reduction of the bacteria. Although the small size of viruses makes gene insertion more difficult, studies have been initiated to attempt to track the progression of the AIDS virus by changing the cells of the animal to glow when a virus invade. David Benaron, a Stanford researcher, hopes that bioluminescence will be used to track the location of cells altered with gene therapy. This research could also illustrate whether these cells were producing the proper proteins after modification. Biologist Woodland Hastings of Harvard University anticipates technological advances allowing surgeons to “localize the cancer and … know where to cut” more effectively than their present techniques. By using firefly luciferin, biologists can ascertain the amounts of Adenine Tri-Phosphate (ATP) in plant, animal and bacterial cells. ATP acts as stored energy for these cells and is directly related to the quantity of cells present. In one application of ATP indicates the incidence and amounts of bacteria present in blood or urine samples. Jellyfish aequorin uses calcium instead of ATP for bioluminescence so this aequorin is used in a similar way to determine the amounts of calcium present. Bioluminescent organisms can determine toxicity because the noxious substances reduce the glow by killing the bacteria.

Bioluminescence is used naturally to help animals attract mates, attract prey, camouflage themselves, and to deter predators. Although one artist has worked with scientists to engineer rabbits to glow only to have a radiant rabbit, this application of bioluminescence research is generally considered frivolous. Most synthetic uses of bioluminescence occur in the medical field to further technological advances. Current research includes tracing the path of disease in living animals, analyzing cellular levels of ATP and calcium and advances in gene therapy. Medical professionals hope to be able to use bioluminescence research to fight AIDS, reduce the number of research animal deaths, and to improve the quality of diagnostic tests.

Adaptations of Bioluminescence

There are four main accepted theories for the evolution of bioluminescent traits:

1. Camouflage
2. Attraction
3. Repulsion
4. Communication

Camouflage

Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples include a tiger's stripes and the battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'                    

 

Anolis caroliensis showing blending camouflage and counter-shading.   A flounder blends in with its environment  A crab is nearly lost in his surroundings  A green lizard is harder to see in the grass

 

Attraction

Bioluminescence is used as a lure to attract prey by several deep sea fish such as the anglerfish. A dangling appendage that extends from the head of the fish attracts small animals to within striking distance of the fish. Some fish, however, utilize a non-bioluminescent lure.The cookiecutter shark uses bioluminescence for camouflage, but a small patch on its underbelly remains dark and appears as a small fish to large predatory fish like tuna and mackerel. When these fish try to consume the "small fish", they are bitten by the shark.Dinoflagellates have an interesting twist on this mechanism. When a predator of plankton is sensed through motion in the water, the dinoflagellate luminesces. This in turn attracts even larger predators which will consume the would-be predator of the dinoflagellate.The attraction of mates is another proposed mechanism of bioluminescent action. This is seen actively in fireflies who utilize periodic flashing in their abdomens to attract mates in the mating season. In the marine environment this has only been well-documented in certain small crustacean called ostracod. It has been suggested that pheromones may be used for long-distance communication, and bioluminescent used at close range to "home in" on the target.The honey mushroom attracts insects using bioluminescence, hoping the insects will help disseminate the fungus' spores into the environment.

Repulsion

Certain squid and small crustaceans utilize bioluminescent chemical mixtures, or bioluminescent bacterial slurries in the same way as many squid use ink. A cloud of luminescence is expulsed, confusing or repelling a potential predator while the squid or crustacean escapes to safety.

Communication

Bioluminescence is thought to play a direct role in communication between bacteria (quorum sensing). It promotes the symbiotic induction of bacteria into host species, and may play a role in colony aggregation.

Purpose of quorum sensing

The purpose of quorum sensing is to coordinate certain behaviour or actions between bacteria of the same kind, depending on their number. For example, opportunistic bacteria, such as Pseudomonas aeruginosa can grow within a host without harming it, until they reach a certain concentration. Then they become aggressive, their numbers sufficient to overcome the host's immune system and form a biofilm, leading to disease. It is hoped that the therapeutic enzymatic degradation of the signaling molecules will prevent the formation of such biofilms and possibly weaken established biofilms. Disrupting the signaling process in this way is called quorum quenching.

Bioluminescence Basic Organisms

Bioluminescence

Bioluminescence is a form of chemiluminescence, which is the production of visible light by a chemical reaction. When this kind of reaction occurs in living organisms, the process is called bioluminescence.

 It is familiar to most of us as the process that causes fireflies to glow. Some of us may also have seen “foxfire,” which is caused by bioluminescence in fungi growing on wood.

Bioluminescence is relatively rare in terrestrial ecosystems, but is much more common in the marine environment. Marine organisms producing bioluminescence include bacteria, algae, cnidaria, annelids, crustaceans, and fishes.

The production of light in bioluminescent organisms results from the conversion of chemical energy to light energy. The energy for bioluminescent reactions is typically provided by an exothermic chemical reaction. Bioluminescence typically requires at least three components: a light-emitting organic molecule known as a luciferin; a source of oxygen (may be O2 , but could also be hydrogen peroxide or a similar compound); and a protein catalyst known as a luciferase. In some organisms, these three components are bound together in a complex called a photoprotein.

Light production may be triggered by the presence of ions (often calcium) or other chemicals. Some bioluminescent systems also contain a fluorescent protein that absorbs the light energy produced by the photoprotein, and reemits this energy as light at a longer wavelength. Several different luciferins have been found in marine organisms, suggesting that bioluminescence may have evolved many times in the sea among different taxonomic groups. Despite these differences, most marine bioluminescence is green to blue in color. These colors travel farther through seawater than warmer colors. In fact, most marine organisms are sensitive only to blue light.

BIOLUMINESCENT ORGANISMS

 

KILLUMINATION

 

Hundreds of meters down in deep, pitch-black ocean waters, monstrous-looking ANGLERFISH wave about bioluminescent lures, called esca, to temp prey into swimming within striking distance. Like fireflies, these common deepwater fish may use the lighting effects in mate selection, as well.

The anglerfish is unusual among bioluminescent creatures in that it does not make its own light chemically; rather, it hosts colonies of symbiotic, light-producing bacteria in its fleshy lure.

 

 

FLYING WITH FIRE

 

The power to make its own light distinguishes the life—and death—of the familiar firefly. Also commonly called lightning bugs, these species have developed unique call-and-response patterns of flashes between courting, airborne males and the females that watch from leafy perches. But danger lurks in this bioluminescent Morse code: Female fireflies in the Photuris genus, for example, mimic the flash responses of females in the Photinus genus, tricking love-seeking, smaller Photinus males into becoming a light meal.

The firefly enzyme Luciferase catalyzes the formation of a Luciferin and ATP complex known as Luciferyl adenylate. This complex is oxidized by oxygen, leading to the production of a cycle peroxide that eventually becomes high-energy Oxyluciferin. The oxyluciferin is initially in an excited state; by relaxing back to the ground state, energy is released and light is emitted.

luciferin + ATP → luciferyl adenylate + PPi
luciferyl adenylate + O2 → oxyluciferin + AMP + Light.

 

GELATINOUS GLOW

 

Comb jellies, technically known as ctenophores, are a phylum of seafaring organism characterized by their use of small hairs, or cilia, for aquatic locomotion. Almost all of these blobby beings also bioluminesce, and they provide yet another example of defensive lighting with so-called "sacrificial tags". Chunks of ctenophores bitten off by predators will keep glowing in the predator's translucent guts, highlighting the gobbler in the ocean's gloom. 

 

EFFULGENT FUNGI

 

Mushrooms gleam in forests all over the world, from the Mycena lucentipes species seen here, described in Brazil last year, to the honey and jack o' lantern mushrooms that emit a greenish "fox fire" glow in woodlands. Researchers have now documented more than 70 species of bioluminescent fungi, although the exact purpose of the 'shrooms' bioluminescence remains mysterious. For species in which just the spore-containing cap shines, the glow may help get the attention of nocturnal bugs that then aid in spore dispersal, similar to brightly colored fruit that draws in frugivores to spread pollen and seeds. Other species with radiant mycelia, or threadlike, vegetative parts, may deploy bioluminescence defensively to attract the predators of the insects that dine on the mushrooms

 

BLUE TIDE

 

Much of the brightness that is observed on the surface of the oceans is due to the bioluminescence of certain species of dinoflagellates, or unicellular algae, and this bioluminescence accounts for many of the recorded observations that have described the apparent "phosphorescence" of the sea. Dinoflagellates are very sensitive to motion induced by ships or fish, and respond with rapid and brilliant flashes, thus causing the glow that is sometimes seen in the wake of a ship. The luciferin in these instances is a tetrapyrrole containing four five-member rings of one nitrogen and four carbons, and its oxidation , catalyzed by dinoflagellate luciferase, results in blue-green light centered at about 470 nanometers (1.85 × 10 ⁻⁵ inches)

PHOTONIC CAMOUFLAGE 

Even in ocean depths where sunlight barely penetrates, the faint silhouette that a fish throws to predators beneath it in the water column can make it an easy target. Accordingly, many fish, crustaceans and squid have developed bioluminescent "counterillumination" abilities. Light-emitting organs called photophores line their undersides. These creatures can adjust the light output of these organs to match the light their eyes receive from above to help eliminate their shadows. The hatchetfish, shown here, is one such species equipped with an underbody that lights up to camouflage it from hungry eyes below.

 

SPARKLING SLIME

 

Dozens of earthworm species from all over the world can secrete a glowing slime, thought to startle predators. This particular worm, Diplocardia longa, is found in sandy soils in southern Georgia in the U.S. and can stretch to over half a meter in length.