Physiology of bioluminescence

bioluminescence - mechanism - organisms involved - applications

1. PHYSIOLOGY OF BIOLUMINESCENCE BY, K.Thangamallika , I M.sc., Microbiology

2. INTRODUCTION: Bioluminescence is the production and emission of light by a living organism. Bio means “living” in Greek and Lumen means “light” in Latin. During this process, chemical energy is converted to light energy. All bioluminescent organisms use a reaction between an enzyme and a substrate to make light, but different species use different chemicals in the process.

3. FIREFLIES It appears to be a warning signal to predators.

4. OCCURRENCE: Bioluminescence on land and in freshwater is rare compared to is occurrence in the ocean. In the deep ocean 90% of the animals are luminescent. Most marine animals that emit light exhibit blue green luminescence. Organisms on land glow mainly in blue green colors, but they can also glow in colors on yellow spectrum. Produced by the organisms themselves and by bacterial symbionts .

5. ORGANISMS: Bacteria ( Vibrio harvii ) Dinoflagellates ( Pyrocystis fusiformis ) Fungi ( Panellus stipticus ) Coelenterates and Ctenophores (jelly fish) Anelids (bristle worms) Insects (fireflies) Sharks (rare) Fishes (many different types).

6. MECHANISM: Bioluminescence is a product of chemical reaction in organisms. Three ingredients are needed for bioluminescence to occur : 1. Luciferin 2. Luciferase 3. Oxygen

7. In the presence of oxygen, the enzyme LUCIFERASE acts upon LUCIFERIN to produce energy. The Luciferase allows oxygen to combine with Luciferin . This reaction produces light and oxidized luciferin become Oxyluciferin . In some reaction do not involve this enzyme luciferase , so these reaction involve chemical called Photoprotein .

8. BIOLUMINESCENCE IN BACTERIA: All bacterial luciferases are approximately 80KDa heterodimers containing two subunits : α and β . The α subunit is responsible for light emission. The lux A and lux B genes encode for the α and β subunits respectively. In most bioluminescent bacteria, the luxA and luxB genes are flanked upstream by luxC and luxD and downstream by luxE .

9. The bioluminescent reaction is as follows: FMNH 2 + O 2 + R-CHO →FMN + H 2 O + R-COOH + Light . Molecular oxygen reacts with FMNH 2 and a long chain aldehyde to produce FMN, water and a corresponding fatty acid.

10. APPLICATIONS : The function of bioluminescence are for : 1. Defence 2. Feeding 3. Communication 4. Mating Bioluminescence plays an important role in the ecology of the ocean.

11. 1. Defense: Certain squid and small crustaceans use bioluminescent chemical mixtures or bacterial slurries in the same way as many squid use ink in order to distract their enemies. 2. Feeding: Use their light to lure prey towards their mouth. Eg : Angler fish

12. 3. Communication: Communication plays a major role in the regulation of luminesence in many species of bacteria and also in fireflies. 4. Mating: The attraction of mates is seen actively in fireflies as well as in ostracods , which use periodic flashing in their abdomens ito attract mates in the mating season.

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