BIOLUMINESCENCE

1. BIOLUMINESCENCE Submitted by, SELMA ABDUL SAMAD BCH- 10 – 05 – 02 S2 MSc BIOCHEMISTRY

2. Phenomenon of production and emission of light by a living organism. • Creatures ( unicellular bacteria to vertebrates ) chemical energy Light energy (Wilson and Hastings, 1998) • Bioluminescent animals Are mostly - marine Very few - terrestrial • Process is 100 % efficient

3. It is different from fluorescence • Fluorescence – Needs high energy radiation The molecule absorbs a photon and excites an electron It comes back to low energy state releasing energy in the form of light.(Williamson & Cummins,1983) The original molecule is restored following fluorescent emission. • Bioluminescence – A characteristic chemical reaction takes place in the organism which releases enough energy producing a visible photon of light. The expended molecule must be replaced by synthesis or diet, it is not regenerated.

4. Chart from lap as on page 1

5. Next chart as on page 2

6. Luciferins • From different biological sources - chemically unrelated • They are polycyclic aromatic compounds that are inherently fluorescent since their orbitals have multiple energy levels. • Bacterial luciferin – a derivative of riboflavin • Dinoflagellate luciferin – related to the chlorophyll structure • Firefly luciferin – Requires ATP for bioluminescence • Coelenterazine – extremely common,found in several species • Vargulin – found in some shrimp species (Vargula & Cypridina)

7. Structures of luciferins as on page 2

8. The spectrum of radiation observed in bioluminescence is very broad • ranges from violet to red • most common are blue or blue green (~470 nm) • This may be because the phenomenon is largely prevalent in oceans ; and seawater is especially transparent to blue light ; Since other light do not travel far in water , evolution might have selected blue color in bioluminescence.

9. Thecolor of bioluminescence depends on • mainly the structure of luciferin (Wilson & Hastings,1998) • 3D structure and amino acid sequence of luciferase protein • The presence of accessory proteins or other chromophores also affect the spectrum of radiated light (Wilson & Hastings,1998)

10. Physiological control of bioluminescence • Complicated • Involves wide variety of mechanisms for subcellular localisation, signal induction & chemical regeneration. • Eg. Bioluminescent bacteria – the photochemicals are present throughout the cytoplasm and glow continuosly without flashing. • Eg. Fireflies – highly structured specialised light producing organs( the lantern) that is regulated by flow of oxygen to it. • Eg. Dinoflagellates – special light producing organelles (scintillons) regulated by shifts in pH. • Eg. Some worms – flashes controlled by Ca2+ entry into cells (William & Hastings,1998) • Basic principle of bioluminescence is preserved across diverse species. But its physiological implementation is extremely variegated.

11. Uses of Bioluminescence • As a defense mechanism – night time • Two logics a) distract primary predator b) make primary predator visible to larger secondary predator • Eg. Dinoflagellates – have a circadian rhythm of bioluminescence ; trigger light flash when they are mechanically disturbed (wave, motion of fish nearby etc) They bioluminesce and produce beautiful displays during red tide blooms. • Camouflage at mid-ocean depths Where light is still available ~90% of animals in mesopelagic zone (200-1000 m depth) are bioluminescent - Some squids – symbiotic association of biolum.bacteria – uses their bioluminescence to match envir. light

12. Defense mechanism – Daytime Some animals bioluminesce blue on their underbellies – the color blends with blue color of the surface water – thus masks them from the predators lurking below. Repulsion of predators – certain squids and shrimps give out biolum. bacterial slurry,like smoke that repels predators. • Defense mechanism – Terrestrial Eg. Fireflies , centipedes , millipedes , worms Warning potential predators that they do not taste pleasant (They also bioluminesce to procure food) • Procure food Eg. Isistius brasiliensis (cookie-cutter shark) Underbelly bioluminesce except a patch of skin near the throat - appears like a small fish & attracts large predators - suctions to large fish , clamps with teeth into their flesh and cuts and bites off cookie shaped chunk of flesh Some predators lure prey by mimicking their signals.

13. Another eg. : Malacosteus (Black dragon fish) - Has 2 different bioluminescent organs - one produces blue-green light - the other (under the eye) produces long IR (red) light - IR light or red light are invisible to most deep sea animals (other than malacosteus) - Thus it can see its prey without alerting them • Attracting & Signaling Potential Mates - By varying their light output - eg. Fireflies and Deep Sea Angler fish - Signaling by light help choose a compatible mate - Intensity or Frequency of signals help discern the health of the mate. (so stronger evolutionary advantage) eg. Fireflies – light production maybe a continuous glow, a certain frequency of flashes or a sequence of repeated flashes that can alternate in frequency.

14. Communication Betweenbacteria - Bacterial lux operon controls bioluminescence - In many bioluminescent bacteria, it is turned on only when the bacteria are in high cell densities (Quorum sensing – The ability of bacteria to regulate gene expression in response to cell density ) - eg. Vibrio, Photomicrobium etc. (mainly found in seawater and in symbiotic association with fishes like angler fish, flashlight fish, bobtail squid etc)

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18. ThusBioluminescence is an example of convergent evolution – different organisms develop the same physical or functional feature through separate evolutionary routes. • Of greater need to marine dwellers – especially in dark faces of water – they produce light for survival , reproduction , species recognition etc. Not much terrestrial animals – light is abundant and life is restricted to the surface of earth.(fireflies, glow-worms, some larvae, insects, arachnids, annelids , fungi etc) • Also known as cold light emission

19. Fireflies • Photinus pyralis, Lampyris noctiluca etc. Family – Lampyridae About 2000 species Found in temperate & tropical environments Their larvae (glow worms) need wet areas. • Luminescent organs – Lanterns • The luminescent cells of lanterns are close to the cells at the end of tracheoles(that bring O2 and take away CO2 from tissues) • These cells have NO synthase (NOS)activated by a nerve impulse Arginine Nitric oxide • The NO diffuses to lantern cells and blocks cyt.c oxidase and thus inhibits cellular respiration in mitochondria.

20. As such, the O2 content in the cells increase and this turns on light production in peroxisomes. • Peroxisomes contain luciferase and luciferin-ATP (ATP is generated when lanterns are dark) • Luciferin + ATP luciferase Luciferyl adenylate + PPi Luciferyl adenylate + O2 Oxyluciferin + AMP + Light (Light ~560 nm and 100% efficient) When oxyluciferin is of - ketoform -- red / green to red light - enolate from -- yellow-green light • The quick decay of NO probably contributes to the short duration of the flash. • Fireflies produce light from their lower abdomen Green, Yellow or pale-red 510 – 670 nm • Fireflies usually use bioluminescence for sexual selection