Hay infusions and yeast water and growing bacteria

[Alfred001]

I'm reading about the spontaneous generation debate between Pasteur and Pouchet and the paper I'm reading mentions that Pasteur used yeast water and Pouchet hay infusions to see whether they would, after being boiled, grow microorganisms upon exposure to air.

 

If you don't know about this debate and spontaneous generation, SG was the idea that organisms could arise spontaneously out of organic or inorganic material. It was believed that fermentation may be an example of this, so Pasteur showed that, no, the microorganisms come from air and they facilitate fermentation rather than being hte byproducts of fermentation (generating spontaneously). So the debate was about whether there indeed were germs in the air which Pasteur used to explain for the presence of microorganisms after fermentation.

 

I'm completely ignorant on this so I'm trying to understand why they were using yeast water and hay infusions. As I understand it, for fermentation you need to have a liquid, some germs and something to serve as food for the germs, but why did they use yeast and pond water (which, I understand, is part of hay infusion), wouldn't this only leave room open for questions like whether maybe the yeast or the organisms from the pond water may have survived the boiling and THAT is what grew in the water, not some germs from the air? Why not simply use sugar or something?

 

As I say, I'm completely ignorant on these matters.

Edited May 19, 2013 by Alfred001

[Dekan]

A good post. The experimenters seem to have taken it for granted that "boiling" destroys all life.

So when pond-water is boiled, the water is rendered lifeless - because living organisms can't survive boiling.

 

Is that true though?

 

 

 

 

 

 

 

[EdEarl]

A good post. The experimenters seem to have taken it for granted that "boiling" destroys all life. So when pond-water is boiled, the water is rendered lifeless - because living organisms can't survive boiling. Is that true though?

I would object to being boiled, but some organisms do live in water that is boiling hot.

 

http://en.wikipedia.org/wiki/Hyperthermophile

Edited May 19, 2013 by EdEarl

[CharonY]

The reason they used yeast and hey infusion is because they were not certain what would be required to generate life, if it happened spontaneously. What was know is that boiling liquids would kill of the organisms, as at that point Pasteur showed that without exposure to air, no "alteration" of the water, as they put it, was seen. The alteration being of course clouding of the liquid due to the formation of microorganisms.

Pasteur demonstrated (or rather proposed) in his experiments that particles in the air may have been the carrier of those microorganisms (and he even tried to correlate it by exposing samples to air in different areas which he assumed to be more or less pristine).

Pouchet set up to disprove this notion in his experiments. In his case, he used artificial air, as well as heat-inactivated hey. Remember, a that point they did know nothing about the molecular composition of life, Pouchet assumed that living things contained a kind of life force that would spontaneously give rise to new life without parents. And indeed, he found something growing in his experiment despite the fact that there was no exposure to ambient, the main source of microorganism in Pastuer's experiment. Later Pasteur would find that there were sources of contamination in Pouchet's experiments, though.