Chapter 6: Energy Flow in the Life of a CellBizarre Facts in Biology |
A test for bacterial contamination uses the glow produced in fireflies to look for possible “hot spots” of bacterial growth. Companies have even developed portable luminometers to check for bacterial growth in water, on food-handling surfaces, and following sewage remediation.
How does this work? This technology is known as ATP (adenosine triphosphate) bioluminescence. As you learned in this chapter, ATP is a high-energy molecule that is produced and used as “energy currency” in all types of cells. Bioluminescence refers to the production of light by living organisms, such as the firefly, certain bacteria, and many aquatic organisms. These organisms give off light for a variety of reasons—to escape predators, to attract prey, and to catch the attention of mates.
So what is ATP bioluminescence? How can the amount of bacteria on a surface or in water be measured quickly and economically? By using the same reaction that nature had developed for the firefly and other bioluminescent organisms! The firefly uses a combination of a substrate, luciferin, and an enzyme, luciferase. Electrons are removed from luciferin by the enzyme, luciferase, to produce oxyluciferin and light. The reaction is dependent on ATP. All cells make and use ATP as a source of energy. The amount of light emitted in the reaction can be measured and is directly proportional to the amount of ATP, and therefore, the number of cells.
A luciferin is a general term used for compounds that have light-emitting capabilities. Bioluminescent organisms produce diverse colors of light because their luciferin and luciferase are chemically different from each other.
An interesting fact is that this light-emitting reaction is very efficient. Very little energy is lost as heat, and so the production of light is referred to as “cold light.”