Scientists estimate that 30 to 40 bioluminescent chemical compounds exist in living organisms such as beetles and bacteria. Of those, we only have good knowledge of about five, says Dimitri Deheyn, a marine biologist at Scripps Institution of Oceanography.
Recently Deheyn and a team of researchers, including three from Connecticut College, took on the challenge of studying the mysterious luminescent mechanisms behind a common marine worm that hasn’t been studied in more than 50 years. The “parchment tube worm,” or Chaetopterus variopedatus, fluoresces a green glow when stimulated by ultraviolet light. It also releases puffs of mucus that give off a long-lasting blue glow. The worm spends its life in a self-made sediment tube, and its habitat ranges across most of the world’s oceans.
The mucus is unique partly because of its longevity and partly because of its color. In the sea water in which the segmented worms live, bioluminescence from other organisms usually appears in fleeting green flashes. In contrast, the glow of the mucus can last up to several hours. And it glows blue.
When the researchers analyzed the mucus, they found that its chemical composition differs from that of any other known biological light-producing compound. “One or two of the proteins are totally unknown,” Deheyn says.
Even stranger, of the known proteins in the mucus, none match anything associated with light production other than vitamin B2, or riboflavin, which creates green fluorescence in bacteria. The riboflavin causes the worm’s body to glow green, but researchers don’t understand how a green fluorescent compound can create blue light.
Since plants and microbes are the only organisms that naturally produce riboflavin, the worm relies on obtaining the vitamin through its diet. However, the researchers also guess that the worms could be obtaining riboflavin through symbiosis between the worm and riboflavin-producing bacteria, which could possibly live in the worm’s sediment tubes to provide a steady supply of the vitamin.
Additionally, the mucus is the first discovered case of bioluminescence that does not depend on the presence of molecular oxygen. The results were published online in October 2013 in Physiological and Biochemical Zoology.
The researchers now have to decipher the chain of chemical reactions that enables the mucus to produce a blue glow. Once they figure this out, the light-producing substance could be integrated into materials where molecular oxygen is not present. The worm’s special luminescence seems especially promising for the field of medical biotechnology, where scientists are exploring bioluminescence imaging. This technique provides the means to monitor physiological processes within the body in real-time by allowing the luminescence to travel within cells. Researchers already use bioluminescent imaging to detect cancers and other diseases in their earliest stages.
- Julianne Chiaet