2009 Pepe Cerasuolo

Here's one. Digging down in response to your query, though, it looks as though H2 is unlikely to be a product of either alcoholic or malo-lactic fermentation (though it can be produced from a lactic acid substrate).

This reference gives a more straightforward explanation of H2S created in wine as a "sulphate reduction sequence pathway act[ing] as an intermediate in the biosynthesis of sulphur-containing amino acids." This explanation is a similar to what Bruce wrote, with the emphasis on amino acid sythesis, though, rather than break-down. I guess if the S for the synthesis is taken from the grape cells, these two processes are related.

Apparently, a form of rocket fuel (N2H4) is produced as an intermediary during anaerobic ammonia oxidation by one aquatic bacterium - even more surprising than H2 production.
 
originally posted by Ian Fitzsimmons:
"sulphate reduction sequence pathway act[ing] as an intermediate in the biosynthesis of sulphur-containing amino acids."
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So that is a totally reasonable pathway related to what Bruce mentioned, but as he also mentioned, it is probably more the breakdown of the amino acids than their synthesis that is the issue.

I believe this is why people who are so inclined add DAP to fermentations.
 
originally posted by Ian Fitzsimmons:


Apparently, a form of rocket fuel (N2H4) is produced as an intermediary during anaerobic ammonia oxidation by one aquatic bacterium - even more surprising than H2 production.
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Oh, you can get a little hydrazine from the odd Gyromitra if you are interested.
 
Actually, having now browsed, H2 production by fermentation seems to be a somewhat fashionable study topic at the moment, in the context of hydrogen cells as an alternative to oil/coal-derived energy.

Sorry to keep editing and crossing your replies. Poor form.
 
originally posted by Ian Fitzsimmons:
Actually, having now browsed, H2 production by fermentation seems to be a somewhat fashionable study topic at the moment, in the context of hydrogen cells as an alternative to oil/coal-derived energy.

Sorry to keep editing and crossing your replies. Poor form.
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Not to worry.

So "fermentations" can produce an amazing variety of things, but what actually happens depends a lot on the circs. The energetics of producing different things depend on the environment. Your critters fermenting at 100* in an acidic geyser in Yellowstone make different things than your critters fermenting next to a sulfur vent at a mid-ocean ridge, who make different things than the carbonic carignan guy, who makes different stuff than the brown-must veltliner producer. The ease with which you make different things depends heavily on the pH, the supply of nutrients, the availability of oxygen, the availability of sulfur, etc., etc. Every "fermentation" is different.
 
Many red-ox pathways to powering ATP formation. Recent thinking, I think, is that cellular life probably originated around the sea vents, arriving at photosynthetic carbon-fixation subsequently. Not to get too far off-topic.
 
originally posted by Ian Fitzsimmons:
Many red-ox pathways to powering ATP formation. Recent thinking, I think, is that cellular life probably originated around the sea vents, arriving at photosynthetic carbon-fixation subsequently. Not to get too far off-topic.
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That's not exactly recent thinking. The proposal was first put out there about 20-30 years ago and has gained momentum with the discovery of various archaea that proliferate under such conditions. The real issue now is to tie up the abiogenesis of nucleic acids and amino acids under such conditions.

Mark Lipton
 
I guess it depends on how you define recent. Is there a more recent theory?

Abiogenetic creation of amino acids was demonstrated in the Miller-Urey experiments of the 50s, and amino acids are also found on meteorites, as you know. There's also a fair amount of argumentation in place about spontaneous occurrence of RNA in early terrestrial conditions. So some of the conceptual pieces are in place, but the details and evidence chain are still works in progress. Right?
 
originally posted by Ian Fitzsimmons:
I guess it depends on how you define recent. Is there a more recent theory?

Abiogenetic creation of amino acids was demonstrated in the Miller-Urey experiments of the 50s, and amino acids are also found on meteorites, as you know. There's also a fair amount of argumentation in place about spontaneous occurrence of RNA in early terrestrial conditions. So some of the conceptual pieces are in place, but the details and evidence chain are still works in progress. Right?
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The Miller-Urey experiments relied on a set of assumptions about prebiotic conditions that have since been completely invalidated, but there are certainly demonstrations of abiotic alpha amino acid synthesis. Peptide synthesis is another story, though progress has been made on the thermal vent front (COS is used to convert carboxylic acids to active esters und so weiter). Much has been made of the "RNA world" hypothesis, but so far the links to phosphodiester formation are sorely lacking.

Mark Lipton
 
Okay, Miller-Urey made inaccurate assumptions about conditions, but their work still demonstrated abiogenetic amino acid formation. Amino acid formation on meteorites, albeit extra-terrestrial, would tend to corroborate (unless, I guess, you are a panspermian).

Sutherland has made some new advances in pre-biotic nucleoside (this is a grant review, sorry, I can't link to the related paper) and nucleotide formation (what I think you mean by phosphodiester formation). If it's possible to establish RNA formation and the presence of amino acids, together with persistent energy gradients (caused by the vents), the evolution of coordinated polypeptide formation by stochastic process, over geologic time scales, doesn't seem ridiculous. Imho.

Anyway, it's interesting stuff.
 
originally posted by SFJoe:
Don't forget to solve the chirality problem, too.
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Sutherland addresses it; the grant link gives the most succinct version. Or rather, he writes about how it plays a role in the sythesis of nucleoside precursors; I don't think he explains its occurance.

The discussion still rather speculative, but how do you prove events of 4 billion years ago without forensic evidence?
 
originally posted by Ian Fitzsimmons:
originally posted by SFJoe:
Don't forget to solve the chirality problem, too.
Click to expand...

Sutherland addresses it; the grant link gives the most succinct version. Or rather, he writes about how it plays a role in the sythesis of nucleoside precursors; I don't think he explains its occurance.

The discussion still rather speculative, but how do you prove events of 4 billion years ago without forensic evidence?
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"Prove" is a high standard.

But you can exclude lots of things, and make a case for others that gets stronger.

The old "RNA World," for instance, explains all sorts of crazy legacy biochemistry--why are ribosomes made of RNA, for instance? Ab initio, no reason at all you'd design it that way. Or why is NADH the unit for small redox exchanges? And so on and on. Doesn't "prove" a particular story, but it makes you think. There might be more forensic evidence around than you thought at first, once you look at things the right way.
 
originally posted by Ian Fitzsimmons:
originally posted by SFJoe:
Don't forget to solve the chirality problem, too.
Click to expand...

Sutherland addresses it; the grant link gives the most succinct version. Or rather, he writes about how it plays a role in the sythesis of nucleoside precursors; I don't think he explains its occurance.

The discussion still rather speculative, but how do you prove events of 4 billion years ago without forensic evidence?
Click to expand...

As my esteemed colleague Dr. SFJoe explains, proof is a high bar, but one can set up experiments to mimic prebiotic conditions (as best we understand them) and see if one can obtain the needed outcome under those conditions. It doesn't prove anything, but it does provide a cogent line of reasoning to explain the outcome. This is after all what Miller and Urey set out to do.

Mark Lipton
 
originally posted by Ian Fitzsimmons:
originally posted by SFJoe:
Don't forget to solve the chirality problem, too.
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Homochirality.
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A guy I know has been doing some pretty interesting work on this lately. I've only seen it presented as a talk, but here are a couple of papers:

Ronald Breslow and Zhan-Ling Cheng, “L-amino acids catalyze the formation of an excess of D-glyceraldehyde, and thus of other D sugars, under credible prebiotic conditions.”
 
Proc. Natl. Acad. Sci. USA. 2010; 107:5723-5725.

Ronald Breslow, Mindy Levine, and Zhen-Ling Cheng, “Imitating Prebiotic Homochirality on Earth,” Orig. Life Evol. Biosph. 2010, 40, 11-26.

The origin of the enantiomeric excess is synchotron radiation from an accretion disc or a neutron star in the galactic neighborhood, which I personally find satisfying. Maybe that's because I don't know as much astrophysics as I should.
 
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