by Melissa Miao
On a warm summer night, children fill the darkness with their laughs of delight as they run to capture fireflies in their glass jars. The glow emanating from the fireflies seems to reflect the glow of pleasure flashing in the children's eyes. But this luminescent jar contains more than a source of childhood fascination, it also holds a treasure of much scientific value.
The fancy name for the fireflies' awesome glow is bioluminescence. This glow-in-the-dark phenomenon is not only found in fireflies, but also in many other organisms. In 77 A.D., one of the first naturalists, Pliny the Elder, discovered a clam that could squirt a light-emitting liquid that would make one's mouth glow when eaten. When the rest of Rome found out about this, a fad of glow-in-the-dark banquets soon followed. This example shows how people found ways to take advantage of bioluminescence, even before advanced scientific methods were developed.
However, today's scientists are exploring ways to apply luminescent reactions to other, more serious situations. One focus is on the gene that makes fireflies glow. The fireflies' light organs are like combustion chambers which consist of three main substances: luciferin (one of the fireflies' glowing genes), luciferase (an enzyme that speeds up the reaction), and ATP (a protein which supplies energy needed for organisms to survive). When they all combine with oxygen, a high energy molecule is created. In order to return to its normal state, the firefly releases the extra energy as light, which is then radiated from the fireflies' bodies.
By combining any two of these three substances, researchers can test for the presence of the third by observing whether or not there is a glow. In certain applications, scientists have used the firefly gene and enzyme to test for ATP--the molecule that has always been associated with providing energy for living organisms. Since the presence of ATP is essentially proof of life, itself, NASA has considered using this method as an indicator of life on other planets! For example, Martian soil could be mixed with firefly compounds and if the mixture glowed, there would be proof of ATP and, therefore, life.
Biologists are also using the bugs' soft yellow glow to identify more effective treatments for tuberculosis. This is a vital issue because the tuberculosis-causing bacteria are becoming resistant to current treatments and new ones must be developed. The firefly enzyme luciferase is injected into tuberculosis bacteria grown in culture dishes, and then an antibiotic is added. If the drug fails, the bacteria will continue to live and will glow when luciferin is added, because it is creating ATP. But if the antibiotic is successful, the dead bacteria remains dark. This method enables doctors to cut the time necessary to test drug treatments to just three days, as opposed to the two to three months it used to take.
It is amazing to think that such seemingly insignificant fireflies can be of such importance to science. Just think, the firefly tails lighting up the summer evenings are now also lighting up new hope and brighter promise.
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