Chemistry of seabed's hot vents could explain emergence of life

April 27, 2015
ocean

Hot vents on the seabed could have spontaneously produced the organic molecules necessary for life, according to new research by UCL chemists. The study shows how the surfaces of mineral particles inside hydrothermal vents have similar chemical properties to enzymes, the biological molecules that govern chemical reactions in living organisms. This means that vents are able to create simple carbon-based molecules, such as methanol and formic acid, out of the dissolved CO2 in the water.

The discovery, published in the journal Chemical Communications, explains how some of the key building blocks for organic chemistry were already being formed in nature before life emerged - and may have played a role in the emergence of the first life forms. It also has potential practical applications, showing how products such as plastics and fuels could be synthesised from CO2 rather than oil.

"There is a lot of speculation that hydrothermal could be the location where life on Earth began," says Nora de Leeuw, who heads the team. "There is a lot of CO2 dissolved in the water, which could provide the carbon that the chemistry of is based on, and there is plenty of energy, because the water is hot and turbulent. What our research proves is that these vents also have the chemical properties that encourage these molecules to recombine into molecules usually associated with living organisms."

The team combined laboratory experiments with supercomputer simulations to investigate the conditions under which the mineral particles would catalyse the conversion of CO2 into . The experiments replicated the conditions present in , where hot and slightly alkaline water rich in dissolved CO2 passes over the mineral greigite (Fe3S4), located on the inside surfaces of the vents. These experiments hinted at the chemical processes that were underway. The simulations, which were run on UCL's Legion supercomputer and HECToR (the UK national supercomputing service), provided a molecule-by-molecule view of how the CO2 and greigite interacted, helping to make sense of what was being observed in the experiments. The computing power and programming expertise to accurately simulate the behaviour of individual molecules in this way has only become available in the past decade.

"We found that the surfaces and crystal structures inside these vents act as catalysts, encouraging chemical changes in the material that settles on them," says Nathan Hollingsworth, a co-author of the study. "They behave much like enzymes do in living organisms, breaking down the bonds between carbon and oxygen atoms. This lets them combine with water to produce , acetic acid, methanol and pyruvic acid. Once you have simple carbon-based chemicals such as these, it opens the door to more complex carbon-based chemistry."

Theories about the emergence of life suggest that increasingly complex carbon-based chemistry led to self-replicating molecules - and, eventually, the appearance of the first cellular life forms. This research shows how one of the first steps in this journey may have occurred. It is proof that simple organic can be synthesised in nature without living organisms being present. It also confirms that are a plausible location for at least part of this process to have occurred.

The study could also have a practical applications, as it provides a method for creating carbon-based chemicals out of CO2, without the need for extreme heat or pressure. This could, in the long term, replace oil as the raw material for products such as plastics, fertilisers and fuels.

This study shows, albeit on a very small scale, that such products, which are currently produced from non-renewable raw materials, can be produced by more environmentally friendly means. If the process can be scaled up to commercially viable scales, it would not only save oil, but use up CO2 - a greenhouse gas - as a raw material.

Explore further: Origin of life emerged from cell membrane bioenergetics

More information: Chemical Communications, pubs.rsc.org/en/content/articlelanding/2015/cc/c5cc02078f#!divAbstract

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gkam
3.8 / 5 (4) Apr 27, 2015
Maybe we are not Martians after all?
Torbjorn_Larsson_OM
5 / 5 (6) Apr 27, 2015
Wow! This looks to be a good proof-of-principle paper. [And open access.]

They show that redox potentials in these system, which can be caused by mineral interaction et cetera, can drive a hydrocarbon synthesis at reasonable efficiencies, ~ 8 %. And if, and only if, the vent is alkaline it would maximize in efficiency and molecule length.

Russel et al suggested metabolic pathways would pass this test, and the reasonable efficiencies would strengthen their theory. Even better, while they leave off with 2C acetyl, the proof-of-principle chemistry show that 3C pyruvic acid would be an end member. This would immediately translate to glucose and penthose production by Keller et al pathways. (Under product separation, say by similarly passing pores or semipermeable mineral membranes.) [ http://msb.embopr...725.long ]

[tbctd]
Torbjorn_Larsson_OM
5 / 5 (6) Apr 27, 2015
[ctd]

And who knows what the end products of Keller's pathways are? They didn't go on to check if a product would be, say, purines as today's metabolism.

Comparing efficiency, the ~ 30 % efficiency of Keller's non-enzymatic glucolysis/gluconeogenesis is at least 5-6 times these redox-driven syntheses. The former is about today's metabolic efficiency, and I wouldn't be surprised if methanogenes/acetogenes have the same basic efficiency at initial energy & carbon capture as demonstrated here.

@gkam: No, it looks like we are homegrown! I think I will dive to one of these ancient ancestral geosystems, chemically barren though as they are in our oxic oceans, and say hello. Most are submarine deep, but there are a few coastal analogs outside Iceland that are scuba reachable.
gkam
4.3 / 5 (6) Apr 27, 2015
TL, you are exactly what I had hoped to find in these threads, . . someone with education and experience to share, not silly stuff.

Thank you for the education as well as the enthusiasm.
Tektrix
4.2 / 5 (5) Apr 27, 2015
TL, you are exactly what I had hoped to find in these threads, . . someone with education and experience to share, not silly stuff.

Thank you for the education as well as the enthusiasm.


Heartily agree- kudos for the informed (and thankfully, secular) comments!
Torbjorn_Larsson_OM
5 / 5 (4) Apr 28, 2015
Thank you!

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