Practical Applications of Bioluminescence

The most promising applications of bioluminescence are in the medical field. The high detectability and rapidity of bioluminescence provides the ability to continuously monitor biological processes such as gene expression and disease progression. Bioluminescence imaging (BLI) has emerged as a powerful new method to analyze infectious diseases in a non-invasive way and its application has increased tremendously in the past decade. It has contributed significantly to advances in biomedical research in the fields of immunology, oncology, virology, and neuroscience.

Luciferase systems are widely used in the field of genetic engineering as reporter genes. Genetic reporter systems have contributed greatly to the study of eukaryotic gene expression and regulation. Reporter genes are most frequently used as indicators of transcriptional activity in cells. Typically, a reporter gene is joined to a promoter sequence in an expression vector that is transferred into cells. Following the transfer, cells are assayed for the presence of the reporter by directly measuring the reporter protein itself or the enzymatic activity of the reporter protein.

Bacterial bioluminescence can be used to test for a specific bacterial species or possible food- borne pathogens such as salmonella. The lux gene, responsible for bacterial bioluminescence, has been isolated and cloned. The cloned lux gene can be injected into a host-specific phage, which does not have the ability to express the gene. If the phage infects a host bacterium, light emission results.  Water quality is tested by employing the bioluminescent marine bacteria Vibrio fischeri. When this organism is challenged by a toxin, the respiration pathway is disrupted, resulting in a decrease in bioluminescent intensity.

Scientists are researching other “fun” and practical applications of bioluminescence. Some proposed applications of engineered bioluminescence include glowing trees to line highways to save government electricity bills, Christmas trees that do not need lights, thereby reducing danger from electrical fires, and agricultural crops and domestic plants that luminesce when they need watering.

Why Bioluminescence Doesn’t Occur Naturally in Plants

Plants don't glow in the dark. Bioluminescence doesn't occur naturally in plants. Some plants, like tobacco and the orchid, have been genetically modified so that they can obtain bioluminescence.

Bioluminescence is incredibly taxing on metabolism. While one may be able to splice luminescence into a plant, the glowing plant will be miserable. Plants are not designed to bioluminesce; it would require an enormous amount of energy to maintain all basic plant functions and also bioluminesce. There are many patents for methods to force plants to bioluminesce. One particular patent did cause the plant to produce bioluminescent flowers, but it also introduced sterility. Most of these methods infuse plants’ genotypes with luciferase, but there have also been attempts to infuse plants with aequorin, the bioluminescent chemical found in some jellyfish. With advances in the knowledge of the chemistry and biology of bioluminescence, genetically-engineered bioluminescent plants and animals may become as common on Earth as on Pandora!

Through a very long process of natural selection, bioluminescent organisms have developed the ability to enhance light production through physiological, molecular, anatomical, and behavioral adaptations. This occurs because the bioluminescence imparts an important ecological advantage to the organism. It is the ecological context that provides the driving force for natural selection. In order for an organism to use bioluminescence that has been artificially induced there should be an ecological role for the light emission. To produce light for the wrong reason or at the wrong time would be a deadly mistake. 

The Sea Firefly (Vargula hilgendorfii)

Sea fireflies are totally unrelated to the fireflies on land, in spite of their name. They are crustaceans and have no backbone. V. hilgendorfii is a small animal, only 3 mm long, roughly the size and shape of a sesame seed. The female tends to be larger than the male. It is nocturnal and lives in the sand at the bottom of shallow water. It is both a scavenger and a predator, mainly dining on sandworms and dead fish.

V. hilgendorfii is produces a blue-colored light by a specialized chemical reaction of the substrate luciferin and the enzyme luciferase. It is indigenous to the water off of the southern Japanese coast. V. hilgendorfii is known to the Japanese as “umihotaru” – “umi” means sea and “hotaru” means firefly. Dried sea-fireflies were sometimes used as a light source by the Japanese army during World War II to read maps in the dim light. The primary structure of the mitochondrial DNA of V. hilgendorfii was sequenced in 2004 by two Japanese scientists, Katsunori Ogoh and Yoshihiro Ohmiya.

V. hilgendorfii has a beaklike projection on the front of a smooth, oval, clear carapace. The black eyes are visible through the carapace. The carapace has large notches through which the antennae stick out. The appendages at the tip of the abdomen are very large and visible between the folded halves of the carapace.

V. hilgendorfii remain buried just under the surface of the sand during the day. At night they use their antennae to move across the bottom or swim over the bottom. When threatened they will use the large appendages on the tip of the abdomen to push themselves into the sand. They also use these structures to lift themselves quickly up from the sand and into the water.

Males hold females for about 30 to 60 minutes before mating actually begins. Males transfer a packet of sperm to the female's reproductive organs. Females brood their eggs under the carapace. The larvae molt five times before reaching adulthood. Young larvae are capable of crawling, digging, and swimming.

Bioluminescence in Land Animals

Most of the world's bioluminescence exists in the ocean, not on land. But there are bioluminescent land animals, including insects, centipedes, millipedes and worms. In contrast to the marine environment, where the predominant bioluminescence color is blue, in the terrestrial environment, green is the predominant bioluminescence color.

One of the most widely-known luminescent insects is the firefly. There are more than 2,000 species of fireflies, or lightning bugs, and they are actually winged beetles, not flies.

       

Glow worms are actually just fireflies (Lampyridae) in their larvae stage. Fireflies glow even when they are just tiny, wingless larvae. They radiate a single, unwavering green light on their foreheads which serves as a warning to predators. The larvae of the glow worm beetle, or Phengodidae beetle, are also known as glow worms. The trunks of the females and larvae of these beetles have bioluminescent organs that emit yellow or green light. In the dark, these glow worms glow in a fascinating stripped pattern.

The Diplocardia longa earthworm exudes a sticky, bioluminescent slime when it's disturbed as a way to scare off predators. This excretion contains luciferin, the same light-emitting chemical found in fireflies. The earthworms can grow to be up to 20 inches long and are found in the southern United States.

                                            

The Quantula striata (also known as Dyakia striata) is the only land snail known to produce light. Found in Singapore and Malaysia, the snail's eggs and newly hatched juveniles continuously glow in the dark. As they mature, the snails switch to only glowing in flashes when something disturbs them.

                                              

It is also interesting to note that there are no luminous flowering plants, birds, reptiles, amphibians or mammals.