A form of chemiluminescence happening in living organisms. Chemiluminescence refers to chemical reactions in which the energy produced is given off not as heat but as light. The most familiar example of this "cold light" is the firefly (Coleoptera: Lampyridae family), which use an enzyme called luciferase that triggers a light-emitting reaction, making the insect's lower abdomen glow. Some fungi and earthworms also use bioluminescence, but it is most common in the oceans where fish and worms have glowing organs and use the produced light as a decoy or sometimes as a bait.

Biologists at Cambridge University have recently developed a genetically engineered strain of potato that will help to limit the amount of water used in agriculture by exhibiting bioluminescence whenever it senses a water shortage.

That's right--the potato plants' leaves emit a faint level of bioluminescent light when the plant senses a necessity for water, such that if they are exposed to a blacklight the leaves of the plant would glow "like a white shirt in a disco", Cambridge biologist Anthony Trewavas says. This will allow farmers to selectively identify which potatos require watering and which do not, which will work to preserve water as well as to prevent the loss of vital nutrients such as nitrates that may be washed into plant-inaccessible depths of the soil by overwatering.

Trewavas and associates achieved this feat by inserting a portion of the genetic material of luminescent jellyfish aequorea victoria into a normal strain of potato plant, and then by activating triggers which will allow the plant to better conserve water when it identifies itself to be dehydrating, as well as causing it to activate bioluminescent genes that cause it to glow a faint green.

Bioluminescence is light created by a living organism. The most commonly known example in North America is the firefly, which lights its abdomen during the mating season to communicate with potential mates. The biggest difference between normal light sources and bioluminescent ones is that that the latter form produces light with virtually no heat radiation. It is this fact which caught the attention of early scientists.

Although the firefly does produce bioluminescent light, the are many other examples. Among these types of organisms are bacteria, protozoa, fungi, sponges, crustaceans, insects, fish, squid, jellyfish, and lower plants. Although commonly thought to be a rare process, it is not. Scientists estimate that two-thirds of deep-sea fish are bioluminescent, and a sample of seawater always contains some bioluminescent bacteria.

Most deep-sea fish do not actually posses bioluminescent abilities, but instead they live in a symbiotic relationship with bioluminescent bacteria. One example of this relationship is Photoblepharon palebratus. This fish harbors bioluminescent bacteria in a pocket behind its eye. The light from the bacteria allow these fish to stay together in schools while traveling, and are used to improve sight while hunting.

Scientists believe that bioluminescence developed independently, and that the genes did not come from any one “Eve.” One of the arguments behind this is the enzyme Luciferase. Luciferase breaks down FMnH2 into chemicals that then oxidize and release photons of light. The enzyme Luciferase however, has many different forms. For example, the amino acid sequence in the firefly is only similar to 48% of the sequence in the Click Beetle.

Bioluminescence can also be used to diagnose disease. Mycobacterium tuberculosis can take up to three months to grown enough cells for doctors to determine which strain it is that the patient is infected with. Since there are eleven different drugs used to treat tuberculosis, it is very hard to guess which one a patient needs without knowing what strain they have. Genes that cause bioluminescence can be added to the bacteria through a virus. The bacteria will then begin producing Luciferin. Thus, by using a Luminometer doctors can tell which antibiotics kill that specific strain of TB.

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