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.