BIEB132_L6_Bioluminescence

BIEB132_L6_Bioluminescence - Bioluminescence BIEB 132...

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Bioluminescence BIEB 132: Lecture 6, 10/13/09 1. What is bioluminescence? 2. Functions 3. Organisms 4. Applications Reading: Levinton pp. 105, 245, 253; Widder Bioscience Explained 2001 paper (Readings folder of class web site) Additional resources: http://www.lifesci.ucsb.edu/~biolum/ http://siobiolum.ucsd.edu http://biolum.org http://www.biobay.com 1. What is bioluminescence? Definition – biological light emission with an ecological context Features 1. Light generated by a chemical reaction 2. Sometimes produced by symbiotic bacteria 3. Purpose – alters behavior of organism detecting the light – benefits organism producing light 4. Danger – inappropriate use of bioluminescence can make organism vulnerable Importance 1. Involves unique biochemical, physiological, genetic, anatomical, and behavioral adaptations 2. Common form of optical signaling in dim or dark conditions 3. > 90% deep sea animals are luminescent 4. Widespread – found in wide variety of organisms 5. Has applications in science and medicine 2. Diversity of Luminescent Organisms Unicellular – Bacteria, Dinoflagellates, Radiolaria Multicellular Coelenterates – medusae, siphonophores, ctenophores Molluscs – squid, octopus Polychaetes (worms) Crustaceans – copepods, ostracods, euphausiids, shrimp Echinoderms – seastars, brittlestars, holothurians (sea cucumbers) Tunicates – larvaceans, pyrosomes Vertebrates – sharks, fish Terrestrial – Fungi, Fireflies and other beetles, Flies (glowworms) Bioluminescence p.1 of 7
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3. Chemistry of Bioluminescence Light emission results from chemiluminescence Form of electron transfer, creates excited state, decays to ground state emitting photon Luciferin – substrate molecule that is oxidized Luciferase – protein that catalyzes the reaction 1. Oxygenase – requires oxygen, not homologous to other oxygenases Oxygen is required, sometimes other co-factors Energy released as visible light, usually in blue-green (470–510 nm) 4. Luciferins More than 2 dozen different luminescent chemistries, only 7 luciferins described Different chemistries do not cross-react Highly reactive with oxygen and reactive oxygen species (ROS) 1. Evolved as antioxidant Major types of luciferins 1. Coelenterazine – jellyfish, copepods, shrimp 2. Vargulin – ostracods 3. Dinoflagellate-type – derived from chlorophyll, dinoflagellates, euphausiids 4. Bacteria – flavin mononucleotide Source of luciferin 1. Synthesized de novo 2. Acquired through the diet 1. Opossum shrimp Gnathophausia – coelenterazine 2. Midshipman fish Porichthys – vargulin 3. Accumulates in non-luminescent tissue 5. Photoproteins Photoprotein = luciferin + luciferase + oxygen Photoproteins are stable, while luciferins are very reactive Most photoproteins are calcium activated, no additional oxygen required Jellyfish Aequorea 1. Bioluminescence emission is green, while luminescent reaction emits blue light 2. Photoprotein aequorin – calcium activated 3. Energy transfer to green fluorescent protein (GFP) 4.
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