Background
Bioluminescence is the process by which an organism produces its own light due to a chemical reaction. It is sometimes mistaken for biofluorescence, the re-emission of absorbed light in a new color.
Though commonly associated with fireflies and glowworms, the phenomenon is rare in land species. By contrast, an estimated 75% of all ocean animals, including more than half of all jellyfish and two-thirds of squid, exhibit this ability themselves or through a symbiotic relationship with bioluminescent bacteria (see gallery).
Scientists have used the proteins involved in bioluminescence to engineer methods for observing disease progression, controlling brain cells, and identifying biochemical signals within cells for drug discovery.
How It Works
Bioluminescence comes from oxyluciferin, the general name for various energized molecules that emit light. Differences in the composition and structure of oxyluciferin result in the range of colors emitted as it releases its energy.
Just as adding chicken to different salad bases produces various kinds of chicken salads, all oxyluciferins are created by adding oxygen to different starting molecules, called luciferins (see examples).
The chemical diversity of luciferins comes from bioluminescence having evolved independently at least 94 different times in nature—the first instance at least 540 million years ago—much the same way a diverse set of shirts with distinct materials, colors, and patterns would be created if made across various points in history.
An enzyme called luciferase acts as a catalyst that facilitates the reaction by providing a location where oxygen and luciferin can more easily bind together (enzymes, explained). Like a lock needing a specific key to open, each luciferin fits into a particular version of luciferase, which is not universal across species.
Luciferases produce oxyluciferin consistently and generate a steady glow. Rapid flashes of light are instead driven by another class of enzymes called photoproteins, which rapidly catalyze reactions.
Although the color of bioluminescence is limited to the variety of oxyluciferin and the energies they contain, blue light’s greater energy and penetrating power in water likely helped it evolve into the predominant color for oceanic creatures.
Natural Functions
Since bioluminescence originated independently across species, its uses range from mating and communication to hunting and self-defense (see illustrated examples).
Each of the over 2,000 species of fireflies emits light and flies in unique patterns as part of their courtship ritual. In their larval stage, before developing reproductive organs, their emissions are antipredatory and communicate toxicity (learn more).
Pyrosomes, or “sea pickles,” are colonies of multicellular organisms that use light to communicate within the colony and coordinate functions like underwater movement.
Anglerfish and dragonfish contain symbiotic light organs housing bioluminescent bacteria that can emit light to confuse and attract prey.
Some creatures, like pandalid shrimp, spew bioluminescent slush to startle, distract, or misdirect predators. Ostracods, a type of crustacean, release this material upon being eaten to illuminate their predator from within—a burglar alarm signal—forcing their release for risk of alerting larger predators to their attacker (watch the alarm).
Contrastingly, parasites and fungi can use bioluminescence to facilitate being seen, eaten, and spread to other organisms and environments.
Applications
Scientists have modified genes they want to understand with luciferase to create reporter genes. When activated, these genes provide visual cues to help directly monitor protein production, cellular movement, and virus spread (learn more).
Inspired by bioluminescence, synthetic luciferin-luciferase systems have been developed whose emissions can travel through layers of tissue, noninvasively revealing activity in inaccessible regions of organs without harming living test subjects.
Because bioluminescence produces cold light—illumination with very little energy lost to heat—tubes of such microorganisms have been tested as electricity-free street lighting. With efficiencies near 100%, these containers surpass modern LED bulbs' approximately 90% efficiency, though they are less bright.
.png)
