Re: [DIYbio] Making contact to a Professor (Dr. Krichevsky)

I don't know much about the state of this particular company, but what
they're trying to do is pretty hard.

Having used the lux operon before in bacteria, the first thing to note
is that it's pretty dim, even at the maximum output levels in a
healthy, dense culture. It's much less bright than a glowstick, say.
Requiring very dark adapted eyes to appreciate.

Getting a healthy dose of photons out of a biochemical pathway
requires a lot of energy. I imagine simply putting the lux pathway
into plants didn't result in a species bright enough to really impress
a consumer market. It will take a lot of work to direct more of the
plants' resources into the precursors necessary to fuel the
photochemical event.

Almost all bioluminescent systems use a catalytic enzyme called a
"luciferase" that activates a species specific "luciferin" with an
electron-donor that ultimately ends up generating a peroxide
intermediate with strained bonds whose decay is high-energy enough to
cause a singlet-state excitation and quick photo-emission.

The lux system typically only generates 10^3 photons/sec/bacterium,
which can briefly result in a dim glow in a dense oxygenated culture
(10^12 bacteria/mL * 10^3 = 10^15, but only when you shake them to
oxygenate all the cells). Some species of krill and fish can push
10^12 photons from their light emitting organs ~continuously.

Note that 1 lumen is ~ 10^15 photons/sec, and a weak nightlight bulb
is typically around 10^17 photons/sec, so we're talking about subtle
effects here. American fireflies can pulse brighter by controlling
the photochemical reaction rate and can get up to 10^14 photons/sec.
I'm not sure what the bioluminescent record holder is. These bugs
probably control brightness by constricting oxygenation of their
photocytes, wherein the luciferase is found near peroxisomes and the
luciferin is bunched up in cytoplasmic granules.

Here are some general refs:
http://anselmlevskaya.com/papers/bioluminescence.pdf - marine
bioluminescence review
http://www.photobiology.info/Viviani.html - discussion of terrestrial
bioluminescence

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