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Matthew Coghill

on 10 March 2013

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Transcript of Photocytes

What are Photocytes? "Photo" = Light

"Cyte" = Cell

These are cells that can produce light through various biological mechanisms

Occurs in marine vertebrates and invertebrates, as well as fungi, microorganisms and terrestrial animals 1) Photophores with Specialized Peroxisomal Cells Cells contain high amounts of peroxisomes

The peroxisomes contain luciferin (pigment) and luciferase (enzyme)

Luciferase catalyzes luciferin in the presence of oxygen to produce energy in the form of light

Peroxisomes emit blue light around 490 nm Luciferin and Luciferase Luciferin = chemical pigment that changes in a reaction to produce energy in the form of light

Luciferase = Enzyme with 2 terminal domains

N-terminal domain (Beta sheet - Alpha helix & Beta barrel)

C-terminal domain (Beta sheet - Alpha helix)

Domains come together to enclose luciferin Regulation of Oxygen Oxygen regulation controls the luciferin reaction and thus how much light is produced

Surrounding cells can regulate oxygen from blood vessels

Mitochondria absorb oxygen

Control of certain "cofactors" will limit reaction Photocytes in Fungi Foxfire in decaying wood

Glow produced by luciferin reaction

Light attracts insects to spread spores or to warn hungry animals Variations of this process Jellyfish that contain photoproteins (luciferin or aequorin)
Relies on calcium ions

Sea pansy's that contain GFP
Can produce different colors of light depending on conditions What are Photocytes? Photocytes contain enzyme luciferase which catalyzes chemical pigment luciferin in the presence of oxygen to produce colored light

Most common emitted wavelength = 490 nm (blue)

Different layers of epithelial tissue

Can emit light by themselves or in groups

In many species, this reaction uses cofactors such as calcuim, ions, or ATP 2) Photophores containing Bioluminescent Bacteria Some organisms have a symbiotic relationship with bioluminescent bacteria

Bacterial luminescence based on gene expression

Certain bacterial genes will produce light emitting proteins Vampire Squid Lacks an ink sac

Photophores with light producing bacteria cover the body

Concentrated at the ends of the arms

For confusing predators and escaping

FUN FACT: can regenerate arms if one is bitten off Ctenophores The "comb" jellies

Different from true jellyfish

Cilia contain photophores

When cilia beat, original light refracts and emits different colored light 3 Types of Peroxisomal Granules 1) Filled with amorphous matrix and microtubules - flask shaped

2) Large crystal or smaller crystals embedded in the matrix

3) Filled with thick walled tubules Anglerfish Luminescent "bulb" called an escas that acts as a lure...recall Nemo video

Contain bioluminescent bacteria

Bacteria use luciferin and luciferase reaction

FUN FACT: range from 20cm-1 meter in length

Bones are thin and flexible to allow for it to eat larger prey Photocyte Bioluminescent Bacteria Live either on their own or symbiotically in other organisms, as in the Angler fish

Bacteria are responsible for the phenomenon of the "Milky Sea"

Bacteria light up due to being disturbed in the water

FUN FACT: In the first world war, bioluminescence came in handy in sinking a German submarine that had been tracked by the trail of bioluminescence in the water The Glow worm Larval stage glows blue-green color, and fly stage glows yellow-green color

Larval stage spins a nest on the ceiling of the cave and produces strings of mucus to capture prey

Uses its glow to attract food and to burn off wastes

Tail is the actual part of the worm that glows

FUN FACT: in some species the strings of mucous can be poisonous! Dinoflagellates Emit blue-green wavelength

Mechanically stimulated by distrubances in the water, physically and mechanically

Glow used as defense mechanism

FUN FACT: Attracts predators to make them more vulnerable to predators from higher trophic levels The Dragonfish Covered with photophores along lower and upper surfaces of body

Photophores under its eyes and at the end of its long barbel

When disturbed it lights up all over

FUN FACT: Can glow and perceive a red as well as blue-green light

Light is almost infrared and is barely visible to human eye The Purpose of Photocytes 1) Attracting mates ex: fireflies flash abdomen

2) Distraction ex: bobtailsquid expels a cloud of bioluminescence instead of ink

3) Repulsion ex: millipedes

4) Communication ex: bacteria in ocean that turn on genes for light production only when they are at high cell densities

5) Illumination ex: dragonfish that produces red glow

6) Counter-illumination ex: fish species that light up belly to eliminate their shadow References 1) http://ase.tufts.edu/biology/firefly/
2) http://www.economist.com/node/18304146
4) http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artmay98/comb.html
5) http://americandigest.org/mt-archives/grace_notes/small_fires_on_the_deep.php
6) http://yubanet.com/scitech/Scientists-Explore-Living-Lights-on-the-Deep-Sea-Floor_printer.php
7) http://www.waitomo.com/Waitomo-glow-worm.aspx
8) http://www.economist.com/node/18304146
9) http://www.leica-microsystems.com/science-lab/basic-principles-of-luminescence/ Bioluminescence Luciferin and luciferase reactions are characteristic of biolumescence

Biolumescenct organisms produce their own light

Different from fluorescence and phosphorecence

FUN FACT: estimated that 90% of animals in the open ocean are bioluminescent Photophores Photocytes can be grouped together in specialized structures called "Photophores"

Photophore = light emitting organ

These organs can be fairly simple or incredibly complex in structure Photophore PHOTOCYTES
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