Evolution/Adaptation experiment?

[joel]

I'd like to run a table-top experiment to demonstrate evolution/environmental-adaptation for my kids. I'm imagining using yeast, successively transfered to a medium with an increasing concentration of something stressful, on a daily basis. Think that would work? Any idea about what stressor I should use, perhaps salt? Is it reasonable to expect a measaureable adaptation within 2 weeks or a month? Is there a better basic approach for such an experiment? Thanks in advance for your ideas. Cheers!

[UncleAl]

Growth time to log phase for a vat of yeast after innoculation of warm sterile medium is a few hours at most. They really get rocking. Fermenting yeast evlove large volumes of carbon dioxide gas. DO NOT SEAL the vessel! Use a fementation lock (bubbler) for one-way gas conduction.

(As an aside, can you get progessively evolve yeast to grow on "metabolially inert" sucralose sugar substitute by culturing on agar gradients or with high and increasing sucralose concentrations in solution, culturing to exhaustion in low sugar?)

Plate dilute pure yeast culture on a Petri dish. You will grow separated individual colonies with reasonably uniform density (OK - Poisson distribution, but we're talking kids). Do it again, but grow them under a black light hard above the plate (Pyrex is transparent here). A blacklight goes to 345 nm. Do you kill them all off (no fair if it overheated the plate) ? We are in business! Otherwise use a shorter wavelength lamp and be very careful about being burned, especially eyes.

http://www.minershop.com/html/blacklight.html
http://en.wikipedia.org/wiki/Ultraviolet

Photochemistry and Photobiology 81(5) 1047 (2005)
http://phot.allenpress.com/photonlin...5-08-09-RA-645

Expose the yeast after it starts growing. Reproducing cells are most vulnerable. "Mitogenesis causes mutagenesis," Bruce Ames (he of the Ames test.) Are growing yeast in air (aerobic metabolism) more vulnerable than growing yeast in unventilated containment (anaerobic fermentation)?

You can go fancy, as below, or simply regulate total exposure by total time of irradiation. There's a lot of experimentation and exploration possible. Does continuous vs. periodic exposure make a difference? Lots of dimmer vs. less time but more intense? You may want a very dense plating and shoot for 99+% lethality to rapidly breed resistance. Intensity from an infinitely long line source varies as the inverse distance, not the inverse squared distance. Or bulk irradate the bottle of solution culture until it is almost sterilized. Regrow, rezap. Reculture in a new bottle, zap some more.

Make a stepped stack of thin UV-absorbing films. Can you get a gradient of growth of the yeast underneath?. Culture the most zapped colony, replate, repeat the cycle a few times. Do the resulting yeast tolerate much more UV exposure? Are they the same color as when you began?

Raw polycarbonate film cuts off at 220 nm.
A 0.13 mm Mylar (PET) film cuts off at 320 nm.
UV-absorbing polycarbonate film cuts off at 380 nm.

Or go for a stepped stack of very thin, very slightly aluminized or chromed otherwise UV-transparent films as a broadband neutral density filter.

[goku]

i wonder how UA knows so much about yeast and fermentation

[pgrmdave]

I've found that UA tends to know quite a bit about a lot of topics, his knowledge base continues to astound me.

[goku]

Originally Posted by pgrmdave

I've found that UA tends to know quite a bit about a lot of topics, his knowledge base continues to astound me.

you guys been boozen it up have ya, suckin back on grandad's cough medicine

[infamous]

Originally Posted by goku

i wonder how UA knows so much about yeast and fermentation

He's probably got a batch brewing in his bathtub as we speak. Say there Uncle, add a few hops to give it that distinctive bouquet.......................enjoy.

[goku]

Originally Posted by infamous

He's probably got a batch brewing in his bathtub as we speak. Say there Uncle, add a few hops to give it that distinctive bouquet.......................enjoy.

[cwes99_03]

Or he could do what others of us who have a wide ability to understand, and that is Google it when you don't know and come back with the answers. ;-) Suckin on suds sounds good though.

[UncleAl]

add a few hops to give it that distinctive bouquet

Won't work. The active materials in raw hops are intensely unstable to oxidation during storage. Hops must be harvested and quickly boiled to extract active principles and isomerize them to more stable (but still oxidation-susceptible) isomers. Boiling converts essentially insoluble alpha acids into more soluble and stable iso-alpha acids, the bittering substances in beer. Five different naturally occurring alpha acids are isolated from hops: humulone, cohumulone, adhumulone, prehumulone, and posthumulone.

If you drink it, shouldn't you know what is in there and why?

Uncle Al tortured yeast in high school. He released them into the wild when surviving colonies spelled out a supplication (though the innoculation wand may not have been wholly innocent in that).

[Turtle]

Originally Posted by UncleAl

Uncle Al tortured yeast in high school. He released them into the wild when surviving colonies spelled out a supplication (though the innoculation wand may not have been wholly innocent in that).

___What did they supplicate? Help? Freedom? Enquiring minds want to know!