Transcript BIOLUMINESCENCE - The language of Biochemistry

BIOLUMINESCENCE
Submitted by,
SELMA ABDUL SAMAD
BCH- 10 – 05 – 02
S2 MSc BIOCHEMISTRY
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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
It is different from fluorescence
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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.
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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.
Chart from lap as on page 1
Next chart as on page 2
Luciferins
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From different biological sources - chemically unrelated
They are polycyclic aromatic compounds that are
inherently fluorescent since their orbitals have multiple
energy levels.
1.
2.
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4.
5.
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)
Structures of luciferins as on page
2
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The spectrum of radiation observed in
bioluminescence is very broad
–
ranges from violet to red
–
most common are blue or blue green (~470 nm)
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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.
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The color 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)
Physiological control of bioluminescence
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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)
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Basic principle of bioluminescence is preserved across
diverse species.
But its physiological implementation is extremely
variegated.
Uses of Bioluminescence
As a defense mechanism – night time
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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.
2.
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
3.
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.
4.
Defense mechanism – Terrestrial
Eg. Fireflies , centipedes , millipedes , worms
Warning potential predators that they do not taste pleasant
(They also bioluminesce to procure food)
5.
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.
Another eg. : Malacosteus (Black dragon fish)
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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
6.
Attracting & Signaling Potential Mates
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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.
7.
Communication
Between bacteria
- 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)
Pictures
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Pictures
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Bioluminescence
is an example of
convergent evolution – different organisms
develop the same physical or functional feature
through separate evolutionary routes.
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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)
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Also known as cold light emission
Fireflies
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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
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Nitric oxide
The NO diffuses to lantern cells and blocks cyt.c oxidase
and thus inhibits cellular respiration in mitochondria.
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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
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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