Bioluminescence- Light Production in Living Organism

Posted on: October 11, 2006

Bioluminescence- Light Production in Living Organism

Bioluminescence is the phenomenon of light emission by living organisms. You may have observed such phenomena in firefly. Bioluminescence is the result of chemical reactions primarily involving luciferin, luciferase and oxygen. Luciferin is a heat-resistant substrate and the source of light; luciferase- an enzyme, and oxygen is the fuel. Luminescent fungi such as Armillaria mellea and Mycena spp. produce a continuous light in their and mycelium. It is believed that bioluminescent fungi use their light to attract insects that will spread the fungal spores. Luminescent bacteria like Xenorhabdus luminescens also exhibit luminescence.

Biochemistry of Light Production: In 1885, Raphael Dubois, a French physiologist, demonstrated that three substances are involved in bioluminescence: luciferin, luciferase and molecular oxygen. Bioluminescence is due to the substrate enzyme complex of luciferin-luciferase within the cellular cytoplasm. Luciferin is a low molecular weight compound that may be an aldehyde, a polypeptide complex or a protein. Light is produced by the oxidation of luciferin in the presence of the enzyme luciferase (molecular weight 62 kDa). ATP first activates luciferin in the presence of magnesium (Mg2+) and luciferase to produce adenyl luciferin, which is then oxidized to form excited oxyluciferin. During the enzymatic oxidation of luciferin large amounts of energy, 40-80 KCal per mole, become available in a single step, so that the product of the reaction is left in a highly excited state. This product emits light when the excited state returns to the ground state. The reaction is very efficient, some 98% of the energy involved being released as light without production of heat.Applications of BioluminescenceThe phenomenon of bioluminescence is utilized as a valuable scientific tool in many biological experiments.

Space Research: Luciferin and luciferase system can be used in spacecrafts sent to other planets to explore the existence of life. The idea is that a special electronic device would pick up soil from the alien surface and mix it with water, oxygen, luciferin and luciferase. Then if a glow were televised back to earth, we could know that ATP, the fifth requirement for light production, occurs there. The presence of ATP would suggest, in turn the existence of some kind of life in that alien soil.Medical research: The presence of ATP in every living organism has been exploited in medical research too. Injection of luciferin and luciferase exhibit different reactions in a normal and cancerous cell, and can aid in detecting energy problems in human cells. This technique is now used to study heart ailments, muscular dystrophy, urological problems, etc.

Fluorescent marker gene: A marker gene is a short sequence of DNA that acts as a label and it is inserted along with a gene of interest into cells. Fluorescent marker genes make the transformed cells glow under light. Genetic markers enable scientists to choose only the cells that have taken up the target genes and discard others.


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